Root Crops in July

 

 

A fine rutabaga (Swede)!
Photo Produce Market Guide

Root Crops in July

Root Crops to Plant in Central Virginia in July

July is not a good month for sowing many root crops in Virginia – it’s hot and for most fall root crops we can do better waiting till August. Yes, it will still be hot in August, but the daylight is getting shorter and so the hot part of the day is also getting shorter. 

Carrots: if we really need more carrots, we direct sow our eighth bed of carrots in early July. We only do this if they’re really needed, because carrots grown in hot weather do not have the best flavor. They will not be sweet, they may even be bitter.  Our plan is to have grown enough between February and May to last us until late October, stored in perforated plastic bags in the walk-in cooler. But if earlier sowings weren’t all successful, or we ate unusually large amounts of carrots, we can find ourselves sowing them in July.

Use shadecloth to keep the soil damp, or water a lot. Carrot seed will germinate whenever the soil is below 95°F (35°C), provided you can keep the soil damp until the seedlings emerge. You won’t need to do daily watering for long: maybe only 4 days. We flame summer carrots on day 4 after sowing, because we have found that carrots can emerge on day 5 in summer temperatures, despite longer times given in the charts. See Root Crops in May for more about sowing and growing carrots, including pre-emergence flame weeding.

Young kohlrabi plants.
Photo Kathryn Simmons

Kohlrabi: Kohlrabi transplants successfully, unlike carrots and turnips, and this has usually been our method for fall crops. We have sown kohlrabi (Early Purple Vienna and Early White Vienna) in the week beginning July 2, for transplanting 8/3-8/9. Sowing in early August is also possible, for November harvests. Kohlrabi, like other brassicas, can be grown in spring or fall in our zone 7 climate. It’s not actually a root crop, rather a swollen stem, but I’m including it as an “acting root”

Rutabagas: This year we are growing rutabagas (also known as Swedes) again, after several years when we went with more turnips instead. Rutabagas are only sown here in late summer for winter storage. They take longer to grow to a good size than turnips do, so it is necessary to start earlier: 7/15-8/4 here, (mid-August at the latest), allowing 90-100 growing days before a hard freeze. Fall root crops sown too early in the summer can get woody. See the Special Topic for July below for all the details about rutabagas.

Root Crops to Harvest in Central Virginia in July

Potatoes: From mid-June onwards, we can harvest spring-planted potatoes as delicious “new” potatoes. See Root Crops in June for more on this. For maximum yields, hold off on harvesting until two weeks after tops have died. See next week’s post for all the details.

This garden worker loves washing beets!
Photo Wren Vile

Beets: We like to clear all our spring beets by the end of June, but sometimes the job flows over into July. Trimmed beets keep well in perforated plastic bags under refrigeration. Store beets at 32°F (0°C) and 95% humidity.

Carrots: Our third carrots (sown mid-March) should be cleared in early July if not before, and our fourth carrots (sown in late March) and fifth (sown in mid-April) will also be ready to harvest in July. I usually reckon on three months from sowing to harvest for carrots, but they can be faster in warm weather. Don’t leave them in the ground too long, or they will get woody. See Root Crops in June for more on carrots.

Kohlrabi: As with beets, we plan to harvest spring kohlrabi by the end of June, at 3” (7.5 cm) in diameter (or even up to softball size). They get too fibrous if left longer, so we will prioritize getting them up. The base of the globe can be tough, so cut either the wiry root just below the soil surface, or cut higher, leaving a small disc of the globe behind, attached to the taproot.

Turnips:  If we didn’t finish harvesting our spring turnips by the end of June, we really need to get them all up in early July. If we have more than we can eat in the next week, we store them in perforated plastic bags in the walk-in cooler, eating them during the summer. Turnips keep for about 4 months at temperatures close to freezing and humidity of 90-95%. Higher humidity will make them rot (rotting turnips are pretty unpleasant!)

Harvested Purple Top Milan and White Egg turnips.
Photo Pam Dawling

Other Root Crop Tasks in Central Virginia in July:

After all the spring-sown root crops are harvested, and the spring-sown greens have bolted, we prepare the emptied beds for summer or fall crops.

Preparing space for summer-planted crops

In July, we will be looking for beds to plant successions of lettuce, cucumbers, squash and beans; our fall brassica transplants, and our first transplants of fall and winter cabbage and Asian greens. In August, we’ll want beds for our last plantings of cucumbers, squash and beans, the never-ending lettuces, fall beets, turnips, winter radishes, kale, and collards. Harvesting the spring roots promptly and storing them gives us time to prepare the beds for their next crop.

Buckwheat cover crop in flower.
Photo Pam Dawling

Buckwheat

If we have 4 weeks or more before the next crop, we will sow a cover crop of buckwheat in the just-emptied beds. Buckwheat keeps the weeds down and feeds the soil (and the honeybees and other pollinating insects). If there are weeds or lots of crop debris, we will till deep enough to bury that plant matter, then broadcast the buckwheat at a rate of 2–4 oz/100 ft2 (6–12 gm/m2), give another shallow tilling, then water and stand back. If there are no weeds or crop debris, there’s no need to till: you can broadcast the seed, and rake it in before watering (and standing back!). As an alternative to broadcasting you can sow rows of buckwheat with the #22 plate on an EarthWay seeder.

Prepare stale seed beds for fall carrots

If you have less than four weeks before you need to sow or transplant the next crop, you can use the time to kill weeds with the stale seedbed technique. Prepare the bed as if you were about to sow, producing an even surface with a fine tilth (surface texture). Then water as if you had sown something, keeping the surface damp by watering as needed. As soon as you see tiny weeds germinating, hoe the surface very shallowly in sunny breezy weather and let the weeds dry out. Make a last hoeing the day before sowing the next crop. This is especially useful for carrots, scallions or anything with tiny seedlings, which cannot easily compete with weeds.

Another method of germinating and killing weed seedlings when there is no crop in the ground is tarping: cover the bed with an opaque waterproof cover after watering the soil. Weeds seeds germinate, but the weeds cannot grow without light and will die.

Solarizing with clear plastic. Photo Pam Dawling

Solarizing is another approach that works well in hot weather: cover the prepared bed with clear agricultural plastic, such as scraps of a hoophouse covering. The heat of the sun bakes any weed seeds near the surface, and also any disease spores or small pests. Larger creatures such as earthworms can burrow deeper into the soil (as they do anyway in hot weather).

Rutabagas, although these ones don’t have much in the way of necks, a usual distinguishing feature.
Photo Penn State

Special Root Crop Topic for July in Central Virginia: Rutabagas

Rutabagas need to be sown in July in central Virginia. To clarify: rutabagas (known as Swedes in the UK) are Brassica napus, closely related to most other brassica crops. Botanically, rutabagas are part swollen tap roots, part swollen stem (the upper portion of the vegetable which forms the neck, the distinguishing feature of rutabagas). There are secondary roots growing in two rows down the sides of rutabagas. Rutabagas are mostly yellow-fleshed with a tan and reddish or purplish skin, although there are white-fleshed varieties. They all have blue-green waxy, non-hairy leaves. turnips are Brassica rapa, like Chinese cabbage and mustards. Turnips come in a range of colors, white or yellow flesh, with white, purple, red or golden yellow skins. The leaves are bright grass green, usually hairy, and not waxy. Turnips do not have a neck or secondary roots growing off the turnip. Rutabagas have twice the nutrients of turnips. And take longer to grow.

Rutabagas are among the hardiest of vegetables, and can be left growing (or at least not dying) until all other crops have been harvested. The flavor improves after frost. For small plantings, plan on 10’ (3 m) per person. Yields of rutabagas can be 75-180 lbs of roots/100’, (35-80 kg roots/30 m): 50% higher than turnips.

Rutabagas come in very few varieties. Laurentian (95 days OP) has a deep purple crown and cream yellow bottom. The uniform 5–6″ (13-15 cm) roots have sweet pale yellow flesh. Joan (90 days, OP), looks similar to Laurentian, with the added advantage that it is somewhat tolerant to club root. Gilfeather (85 days, OP) is sold as a turnip, but is botanically a white rutabaga. Sweeter and later to mature than turnips, it doesn’t become woody even at softball size. Southern Exposure Seed Exchange also has American Purple Top (not to be confused with the Purple Top White Globe turnip) and the Lithuanian Nadmorska a large oval 90d OP.

Fine rows of rutabagas. See the distinctive necks.
Photo Nan Chase

Keys to growing mild, sweet-tasting rutabagas include cool temperatures, sufficient irrigation, and no competition from weeds or over-crowding. The optimal germination range is 59-95°F (15-35°C). Rutabagas are a little slower to germinate. We sow four rows in 4’ (1.2 m) wide beds. Seeds need to be 0.5” (1.2 cm) deep. When flea beetles or grasshoppers are a problem, use rowcover or insect mesh.

Early thinning is especially important for shapely well-developed rutabagas. Thin to 4” (10 cm) within 10 days of emergence, or at least by 1” (2.5 cm) tall, then to 10” (25 cm) when 2-3” (5-7.5 cm) tall. If not well-thinned, they will grow in odd shapes and be small. 

Boron deficiency causes the middles of the roots to turn brown. Many common weeds are in the Brassica family, and could harbor pests and diseases that could attack the crop, so use crop rotations, stale seedbeds and clean cultivation to remove the weeds.

Aphids, flea beetles, cabbage worms, harlequin bugs, and grasshoppers can all be a problem. Rutabagas have worse trouble with aphids than turnips. Brassica flea beetles are not the same species as the nightshade flea beetles often found on eggplant. Rowcovers or insect netting and the planting of insectaries (flowers to attract beneficial insects such as ladybugs) can help avoid the problems. Bt can be used for the caterpillars, soaps for the aphids and Nolo bait for the grasshoppers (except where banned in order to preserve rare species of grasshopper).

More information 

GrowVeg Rutabaga Growing Guide 

Written in Vermont: Gardener’s Path:

Written in Mother Earth News by Sara Pacher:

DIY Network

The main diseases of rutabagas (and turnips) are club-root, downy mildew, powdery mildew, rhizoctonia rot, bacterial scab, and blackleg. All except scab are fungal diseases. Organic methods of prevention are crop rotations and field sanitation (plowing in residues promptly, removing weeds). Club-root fungus is able to live in the soil for up to 10 years, so is hard to eliminate. Avoid all brassica crops in an affected field for 10 years, and be vigilant about eliminating brassica family weeds. (Develop a fondness for spinach, chard and beet greens!)

Our rutabagas are ready from mid-October. Rutabagas (but not turnips except in warm climates) can be stored in the ground all winter. Mulch over them with loose straw once the temperatures descend near 20°F (-7°C). If you don’t manage to eat all the roots before spring, they will re-sprout and you can have an “early spring bite” of greens (a term more usually used for cattle fodder crops).

Rutabagas can store for as much as 6 months in perforated plastic bags under refrigeration. They do best stored above 95% humidity. Prompt washing before the soil dries on the roots will make them easier to clean later.

In the UK, rutabagas are not waxed as they are in North America. In fact, they store well without waxing, and I encourage you to try skipping the petroleum product.

Sliced rutabaga.
Photo Cornell

Growing High-Yielding Sweet Potatoes

Healthy sweet potato plants. A few insect bites won’t hurt!
Photo Kathryn Simmons

Growing High-Yielding Sweet Potatoes

In May I gave information on planting sweet potatoes. Hopefully that went well for you, and by now you have a large patch of healthy green vines. Let’s keep it that way! Here I will tell you about what the growing plants need, and the pests, disease and afflictions to avoid.

Read more

I have a Sweet Potato slideshow. I have lot of other posts on sweet potatoes (mostly about propagating our own slips, or about harvesting). Click to see the links in last month’s post

The ATTRA publication Sweetpotato: Organic Production is a good introduction.

Oklahoma State University Extension Sweet Potato Production is a clear concise publication (although it’s not organic).

Sweet potato development

This paragraph was included in Planting Sweet Potatoes, and I’m repeating it here, as a good reality check on what you can expect.

Regardless of how early in the season you plant them out, they will not make flowers earlier, or start making tubers sooner. Both flower and tuber initiation are triggered by day length. Each variety has its own internal clock. Most varieties take 90–110 days from planting out to reach a good size, if the weather is warm enough.

The first month or so after transplanting is the root development stage. Roots can go 8’ (2.4 m) deep in 40 days. Don’t be alarmed at the lack of above-ground action. The second month or so is the vine growth stage. The roots begin to store starch and sugar close to the stem base. During the last month of growth for that variety (3rd or 4th month), the potatoes develop. Make sure you dig them up before the soil temperature gets down to 55˚F (13˚C) – the week of the average first fall frost is about right.

Growing sweet potatoes – Three Ws: water, warmth, weed-free
  1. Water
  • The critical time to maintain sufficient moisture is after transplanting for at least the first 20-40 days while roots are developing. By now, most growers will be beyond this most-important watering period. But if it’s less than 40 days since you planted them out, keep the soil moist. Use your fingers to test the soil for dampness.
  • Once they are established, sweet potato plants are fairly drought-tolerant. But if you want high yields, they’ll need water once a week, either from the sky, or provided by you. Note that if you are using plastic mulch, rain won’t go through it, so I hope you installed drip irrigation below the plastic. If not, lay it on top, right beside the plants. Aim to provide an inch (2.5 cm) of water per week.
  1. Warmth
  • Sweet potatoes need warmth! Heat determines success; the number of days from planting does not.
  • Provided the weather is warm enough, most varieties take 90–110 days from planting out to reach a good size.
  • You can gain warmth in a cold climate, by planting inside a hoophouse or low tunnel covered in clear plastic. Ventilate in hot weather.
  • Growing Degree Days (heat units) are a tool for measuring accumulated heat, but you don’t need to calculate GDDs to get a good crop!
  • Early varieties take 1200 GDDs to grow a good crop.
  • To calculate GDDs, take the day’s high temperature (max) and the day’s low temperature (min) and add them together. Divide by 2 and subtract the base temperature of 55F. (Apologies to the rest of the world – I only know this method using Fahrenheit, but I’m sure you can find out how to do the calculations in Celsius). There are phone apps that will do the calculation for you.
  • Example: For a daytime max of 90F, and a night-time min of 70F, you get 25 GDDs – just about perfect for sweet potatoes. 90+70=160. 160/2=80. 80-55=25. At 25 GDDs a day, you theoretically only need about 48 days to get a crop. There are some other limits to daily plant growth – the likely minimum for a decent crop is about 76 days.
  • In a plastic tunnel, you can get 20 GDDs a day or more, rather than the 5 you might get outdoors.

    Water, warmth and no weeds – all that growing sweet potatoes need.
    Photo Nina Gentle
  1. Weed-free
  • Cultivate to remove weeds until the vines cover the ground, after which very little weeding will be needed.
  • If you have plastic mulch, walk through pulling weeds, and drop them on the plastic to cook. If you are growing on bare soil, hoe while the weeds are small, and pull if the weeds and the vines get ahead of you.
  • Weeding is generally not onerous because the sweet potato vines cover the ground within 6 weeks of planting and smother any newly emerging weeds.
Our motion sensor sprinkler and the outer layer of our fence around the sweet potato patch at the end of May.
Photo Pam Dawling
Solar electric fence controller for our sweet potato patch.
Photo Wren Vile
Pest mammals
  • Deer eat sweet potato plants at all stages, including digging out the roots in the fall. Dogs, fences and guns are the three most effective methods of deer control. The plants can be covered with row cover or plastic net for the growing season. Motion-sensor sprayers work well if maintained.
  • Rabbits eat the foliage. Plant the slips on black plastic to hold back weeds, then put wire hoops over the rows and cover with row cover for 3–4 weeks while the plants are young. Even after the plants are large rabbits can cause substantial losses.
  • Groundhogs dig and eat the roots. They can be trapped with baits of fruit. What’s for dinner?
  • Pocket Gophers search out sweet potatoes to eat. Their mounds may be hidden under the foliage and the plants may survive as they only eat the larger roots, leaving no crop.
  • Voles move in from grassy areas to live under the mulch and feed as fast as the roots form. They eat the roots from the top down leaving the outer shell in the soil where they have feasted. Cats are the best control.
  • Rats love the roots. Cats or dogs are the best methods of control.
  • Field Mice build nests under black plastic and eat the roots emerging from the ground.
Why not eat some sweet potato leaves as summer greens?
Photo Nina Gentle
Human “pests” of sweet potatoes

 You can eat sweet potato leaves yourself and it takes several meals to reduce yields of the tubers. Some researchers working in Vietnam, discovered that harvesting 25%, 50%, 75% or 100% of the vines every 15, 20, or 30 days (ignoring the information about the season of the year and the varieties) gave the sort of results you might expect. Harvesting tops every 20 days gave highest yields of greens. Harvesting 50% of the greens each time gave highest total yields of greens. Harvesting not more than 25% or 50% of the greens each time gave the highest eventual tuber yields, after 120 days. Researchers in Tanzania came up with the clear information that harvesting three times at one month intervals gave the highest greens production, but the tuber yield was affected tremendously. Harvesting tops twice in a growing period proved the best in leaf production as well as root yields. So, clip 25-50% of the tops of each plant up to twice in one summer, and you’ll still get a good yield of roots.

Also see the University of Arkansas Extension Nutritional and Medicinal Qualities of Sweetpotato Tops and Leaves. This publication explains how to plant slips 2” (5 cm) apart, specifically for greens (vine tips) and harvest 6 times between the end of April and the end of October.

 Insect pests of sweet potatoes

See North Carolina State University, Pests of Sweetpotato  for photos, drawings and details.

Although there are many insect pests that feed on sweet potato vines and leaves, most do very little damage, and hunting them down is not justified.

Healthy sweet potato patch, with some deer nibbling and weeds..
Photo Wren Vile
Pests that feed on foliage
  • Sweet potato flea beetles – Tiny black/bronze oval beetles (1.6 mm long), with reddish-yellow legs, and ridged wing covers; make small shot-holes in leaves or grooves in the upper surface of the leaves. Damaged areas turn brown and die. See below about larvae.
  • Sweet potato weevil adults and larvae do feed on the foliage, but mostly go for the roots (see below).
  • Caterpillars of three kinds:
    • Southern armyworms – Gray-black larvae up to 36 mm long with green or pink tints; pale longitudinal stripes and pairs of triangular spots along the back; pale yellow heads with bright red-brown marks. They feed on leaves and tips of vines, and congregate around the bases of plants during the middle of the day.
    • Sweet potato hornworms – First instar: white with a black horn; later instars (up to 90 mm long): green or brown with black diagonal lines down each side and a black horn, with a green or brown head with black stripes. They defoliate plants and often hide under leaves near the bases of plants.
    • Yellow-striped armyworms – Pale gray-black caterpillars up to 45 mm long, with orange-yellow stripes along the sides and pairs of triangular spots on the back of most segments; brown heads with black markings and a white inverted V. They feed similarly to southern armyworms.
  • Potato leafhoppers – Wedge-shaped insects up to 3 mm long; green bodies with yellow to dark green spots. They usually jump rather than fly. They suck sap from the underside of leaves causing yellowing of leaf tips and margins.
  • Fruit or vinegar flies – Small yellowish red-eyed flies about 3 mm long. They hover around overripe or decaying produce. They may be found with their small creamy maggots in cracks in sweet potatoes.
  • Tortoise beetle adults and larvae – Long-oval shaped gold beetles, up to 8 mm long, with various black or red markings on their flattened, shell-like bodies. The larvae have dull yellow, brown, or green bodies up to 12 mm long and black heads, legs, spots, and spines. Long spines on the abdomen hold excrement. Adults and larvae chew the leaves riddling them with holes.
  • Spider mites – Tiny reddish or pale spider-like arthropods that feed on the underside of leaves. Heavily infested plants develop a yellowish, bronzed or burned appearance.
Pests that feed underground on tubers and side roots
  • Sweet potato flea beetle larvae – Thin white, cylindrical larvae, up to 5 mm long, with 3 pairs of legs near their heads. They make shallow, winding tunnels on the surface of sweet potato roots and sweet potatoes. The tunnels darken, split, and leave scars.
  • Sweet potato weevil adults and larvae –Snouted beetles 6 mm long with dark-blue wing cases, orange-red legs and thorax, and fat, legless, 9 mm grubby white larvae with pale brown heads. The beetles make small holes over the surface of sweet potatoes mostly at the stem end. The larvae tunnel inside the tubers, leaving frass, which causes the sweet potatoes to taste bitter.
  • White grubs (spring rose beetles) – Dirty white grubs up to 25 mm long with brown heads and 3 pairs of legs near their heads. They leave large, shallow feeding scars on the sweet potatoes.
  • Wireworms – Thin, tough, wire-like larvae with 3 pairs of short legs near their heads and prolegs at the end of the body. They initially create large shallow cavities in sweet potatoes which they later excavate into deep ragged holes. Three species, with colors from yellowish-brown to cream or yellow-grey. Heads are darker, brownish.
  • White-fringed beetle larvae – Yellow-white legless, 12-segmented grubs, up to 13 mm in length, with small, pale heads. They chew into the roots.
Sweet potato souring.
Photo North Carolina Sweet Potato Commission
Afflictions of sweet potatoes (these are not caused by disease organisms) 
  • Round chunky roots, low yield, purple color: Planted too early, too cold.
  • Low yield: Flooded or crusted soil 6-7 weeks after planting? Planted too early?
  • Rough irregular shaped roots: Heavy clay soils or organic matter above 2%.
  • Rattails – thin, tough, tubers: Hot dry weather, insufficient water.
  • Long, slender malformed roots, reduced yield: Potassium deficiency.
  • Souring – Tissue breakdown caused by poor soil aeration, such as flooding.
  • Water blisters – Small whitish bumps around the lenticels (breathing holes): wet soil.
  • Blister – Small raised bumps appearing several months into storage: boron deficiency.
  • Fine hairline cracks: Another sign of boron deficiency.
  • Cracking: Uneven water supply or too much late-season water.
Sweet potato Ring Rot.
Photo North Carolina Sweet Potato Commission
Sweet potato feathery mottle virus.
Photo North Carolina Sweet Potato Commission
Diseases of sweet potatoes (mostly fungal)

 More info and photos: North Carolina State University Diseases of Sweetpotatoes. 

  • Brownish skin patches, worse in wet years: Scurf fungus, Monilochaetes infuscans. More likely if too much compost was used. Stored roots shrivel.
  • Metallic black surface lesions, maybe covering most of the root: black rot fungus, Certocystis fimbriata. Internal decay is not deep, but the fungus may impart a bitter flavor.
  • Sunken brown lesions that may completely encircle the root: ring rot, Pythium
  • Sunken lesions that dry and may fall out: Circular Spot, Sclerotium rolfsii. May taste bitter.
  • Hard, dry, black, sunken spots developing in harvest wounds: Fusarium. Spots may become larger than 2″ (5 cm) diameter, but damage is not deep.
  • Pitting: Soil rot or soil pox fungus in the presence of water stress. Roots will be small and malformed.
  • Streptomyces root rot bacterium causes a similar rot.
  • Fine or coarse irregular cracks, browning of the surface; dry, corky, dark-colored clumps of tissue scattered throughout the flesh, becoming worse if roots are stored warmer than 60°F (16°C): russet-crack/internal cork, feathery mottle virus (yellow feathery patterns of leaves). Do not use as seed stock.
When to harvest sweet potatoes

Unlike white potatoes, which have the annual plant sequence of vegetative growth, flowering and dying back, sweet potato plants would go on growing forever if the weather remained warm enough. Choose when to dig them up, ahead of cold weather. The longer you wait, the bigger the potatoes, but you are gambling with the weather. Usually sweet potatoes are harvested in the week that the first frost typically occurs in your region. I have written plenty already in previous years about harvesting, so I won’t go into it here. See one of the links to those posts, or my slideshow, if you want to know what comes next, or your climate is considerably colder than mine in central Virginia.

Our sweet potatoes next to our sixth sweet corn planting.
Photo Ezra Freeman

Book Review: No-Till Intensive Vegetable Culture, by Bryan O’Hara

Cover of No-Till Intensive Vegetable Culture by Bryan O’Hara

Book Review: No-Till Intensive Vegetable Culture, by Bryan O’Hara

Chelsea Green, 2020. 250 pages, full color photos throughout, $29.95.

Bryan O’Hara’s No-Till Intensive Vegetable Culture is the work of an expert. His bio says he is known for “providing mountains of details in a concise, practical and cohesive manner”, which sounds like my kind of writer!

His book includes science, art, and philosophy. It is an example of something I realized a while ago: if a farmer pays good attention to what works well, and acts in accordance with their observations, it doesn’t seem to me to matter exactly why they think it works! Although I don’t share the author’s spiritual outlook, or practice of Biodynamics, I do highly value healthy soil, diverse ecosystems, crop rotations, nutritious food, good relations with our neighbors and peace in the world. And so I can use the pointers to achieve some of these goals. Bryan has been paying exquisite attention for decades!

This no-till book is very different from Andrew Mefferd’s Organic No-Till Farming Revolution: High-Production Methods for Small-Scale Farmers which I reviewed in May 2019. That book provides a menu of varied methods for those who want to increase the amount of no-till growing on their small-scale farm. Any reduction in tillage is a good step: you don’t have to commit to permanent no-till everywhere. Read Andrew’s book first and choose the reduced-tillage options that suit your farm. Then read Bryan’s book on one particular way of no-till vegetable production and see which parts will work for you.

Bryan and his partner Anita started farming in Connecticut in the early 1990s. Experienced, enthusiastic and energetic, they quickly succeeded, and prepared to expand Tobacco Road Farm. Fortunately, Anita realized the three acres of vegetables they already had was a better fit with their goals: providing for their family year-round, keeping them healthy and happy, providing a service to fellow humans, and freedom from economic subjugation. They embraced Biodynamics as a way to improve crop health, and then Korean Natural Farming. KNF (developed by a Korean, Cho Han Kyu) and making brews of microorganisms (IMOs).

After noticing that tillage was detrimental to their soils, they switched to no-till and were stunned at the differences. The vegetables taste wonderful!

Bryan writes an inspirational narrative, without any fluffy chat. It’s like being in conversation with him. Not everyone can make a discussion of soil quality so engaging! He has a suitable humility about stepping in and influencing the fine balance of the ecosystem. His advice: “be careful not to get in the way of delicate, naturally functioning systems.”

I was surprised to find that Bryan believes that long-lasting condensation trails left by high-flying aircraft under certain conditions are actually “chemtrails” of chemical or biological agents secretly sprayed on us, rather than water-vapor. I do agree that airplane flights significantly add to climate chaos. We who sometimes fly have the responsibility for this, not secret government departments. Like Bryan, I lament the erratic weather, the decline in insect populations, and the struggle to provide water for our livestock and crops in appropriate quantities and rates of distribution.

Bryan describes increasing or decreasing the strength of both or just one side of the growth/reproduction polarity of plant development. Keep the balance of air and water in the soil. Steer things in the direction your crops need. Don’t let the soil dry out, as many life-forms will die, and recovery won’t be instant. But how do we get there from here? Bryan offers suggestions for what to look for when “reading” the appearance of crops in terms of balance. Rank growth? Stunted? Sparse? Obvious nutrient deficiencies? Good yield? Color?

Bryan suggests monitoring the conditions of the soil, air, sunlight and water. Whether you see this as a manifestation of Pagan Earth/Air/Fire/Water elements, or a simple description of aspects of farming doesn’t matter to me. As an example, if you want consistent supplies of an annual cool weather crop, sow several successions in spring (because they will quickly bolt) but fewer in late summer because they will not bolt. Once you understand this, you can follow the cycle of “plan/execute/observe/adjust plan” and get the best possible fit of crops with markets. Your approach may be mystical or pragmatic, but your attention to results will be detailed either way.

If you are drawn to Biodynamics, I think you’ll love this book. If you are drawn to very successful crops, I think you’ll also love this book. You just might skim some it.

The next section of the book is about preparing land for a gradual transition to no-till. Don’t expect to make an overnight change! Try various approaches on small areas. Reduce your tillage until you no longer need any, or just need occasional tillage. Don’t worry that opening a furrow for big seeds, or digging up root vegetables, will get you expelled from the No-Till School! Try to avoid tilling simply to prepare seed beds.

Various conversion methods are explained, even clearing woody growth. First set up a system that doesn’t need primary tillage (usually heavy tractor equipment), but uses secondary tillage tools (rototillers, disk harrows, field cultivators, walking tractors, hand rakes and hoes) for bed prep (and occasional subsoiling to deal with hardpan).

Bryan recommends a three step process for killing old crops or weeds. First is mowing: Bryan most often uses a flail mower on a 16 hp BCS 850. Second is preventing regrowth by solarizing using clear plastic sheeting to heat the soil surface to 125F or more, for a day. Unlike solarizing to kill pathogens deeper in the soil, killing annual crops or weeds is very quick, provided air temperatures are 75F or more. Perennial roots will not solarize quickly – it’s best to remove these before transitioning. Those that arrive later will need digging out, or longer term solarizing using black silage tarps over the winter. For anti-plastic growers, organic mulches of cardboard covered in 2 ft of fresh cut hay can substitute. There is a good review of various mulching materials, and the photos show his own trials. Oak leaves (and coffee grounds) seem to repel slugs!

Mowing or rolling and crimping is another method, given a thick cover crop and good timing. Flaming can work to kill emerging weeds if any mulch is well-watered first. Reading the book will save you trying all the cover-management methods that don’t work well. At Tobacco Road Farm, they now solarize as much as ¼ acre at a time, moving the covers from plot to plot.

The chapter on seeding and transplanting includes a chart of planting methods, seeding rates and spacing for about 65 crops (not just the top twenty!), instructions for hand broadcasting, sowing in rows by hand or by EarthWay. They have learned to get the most from their Earthway, customizing plates, leaning right while pushing, and only half-filling the hopper for round seeds (to avoid the “brassica grinder” effect).

The transplanting section describes clearly how to make use of outdoor nursery seedbeds for growing bare root transplants as we do. For more delicate seedlings February-June, Bryan likes soil blocks on benches under shadecloth or rowcover tunnels.

Watering by hand must be a joy once the farm gets to the point of only needing water for new seeds and new transplants. We’re not there yet, and so must continue dealing with drip “irritation” and sprinklers.

The crop rotation chapter includes a planning chart showing what goes in each plot when throughout the course of a year. The system includes flexibility: if a crop continues to grow well in a spot, it doesn’t get rotated. That challenges one of my cherished beliefs! My next challenge came with the information about the influence of the moon on crop growth. I have raised eyebrows myself, claiming that frosts are more likely with a full moon. It sounds so woo-woo, but it fits my observations. Perhaps Bryan is more observant of details, more woo-woo than me, or both. I’m happy he acknowledges that sometimes a crop needs to be planted regardless of lunar position.

Bryan O’Hara, author of No-Till Intensive Vegetable Culture

Next is a valuable chapter on soil fertility and crop health assessment. This is an area I would like to practice in more. Not just testing pH and the main minerals, but also the Brix measurement of sugar in the crop sap, the electrical conductivity, and soil compaction. Bryan gives a good explanation of cation exchange capacity (the nutrient-holding capacity), and points out the challenges of achieving a good high CEC and then of adjusting the elemental nutrient balance: you need large amounts of material to bring the elements into balance, compared with a low CEC soil. And never forget: “the objective is not to balance a soil test but to get results in the field.” Strong biological activity can outweigh chemical element imbalances.

A slightly acid pH of 6.5 helps cations be more available to the plants: the acidity favors a higher level of fungal activity, which releases nutritional elements held in bonds that resist bacterial action.

Phosphorus buildup is an issue for us growers who use a lot of compost. It is hard for labs to assess phosphorus levels, because many factors influence its soil availability. Compost grows strong plants which in turn reduce water pollution, including phosphorus. Looking at the big picture leads to different solutions than focusing down on soil phosphorus content. Soils high in OM often test high in P because the test includes all the P-containing living fragments. Water-quality regulators are focused on phosphorus contamination of waterways above and beyond that of other pollutants like excess synthetic nitrogen fertilizers and industrial byproducts.

The information on composting is thorough, and Bryan recommends up to 100 tons per acre for a new vegetable patch. Thereafter, 30 tons or more per acre pre-plant. There is a good comparison of various organic fertilizers, and instructions on making bonemeal after cooking meat. There are fish fertilizer recipes which (to my surprise) call for “unprocessed brown sugar.” When I was a hippy grocer in the 70s, our sugar supplier told us there was really no such thing as unprocessed brown sugar – all brown sugars are white sugar with various proportions of molasses added back in. There’s no more nutritional value in brown sugar than in white sugar. Even “raw” sugar isn’t raw. I guess the only unprocessed sugar is a length of sugar cane or a chunk of sugar beet! Is sugar a big evil, like a synthetic fertilizer, that we don’t want to add to our gardens, or does it have a place?

Some growers apply raw manures, or uncomposted food byproducts directly to the soil, (“sheet composting” or “trench composting”) in the fall for crops the following spring. It’s certainly less work than making a compost pile, but is the result as balanced as a composted mix? Everyone has to make their own decisions. Bryan takes a thoughtful look at these options, and milk, seaweed, charcoal, vinegar and more.

He gives us his precise recipes for liquid and solid feeds for seed-starting, for young plants, and for flowering plants; recipes to be modified by growers for their own conditions. He adds particular ingredients to the base recipe of 30% wood chips, 20% dead leaves or straw, 40% cattle manure and 10 % vegetable scraps.

After this we get into the production of Biodynamic preparations, which do seem to require faith. Working barefoot and stirring a bucket of potion to create a vortex is a step too far for me. But for the grower who wants to learn about these techniques from an expert farmer rather than another beginner, this is a good place. Here are recipes for Biodynamic horsetail tea and Preparations 501 (ground quartz) and 500 (horn manure) as well as Oriental Herbal Nutrient (OHN), a fermented herbal preparation, and Fermented Plant Juice (FPJ) from Korean Natural Farming. “With this stirring comes the opportunity to impart the forces of will or prayer into the material, so this is a time of concentration or maybe a song.”

Bryan O’Hara’s Tobacco Road Farm is three acres of intensive vegetable farming at Lebanon, Connecticut.

Next are the Indigenous Microorganisms (IMO). This is part of Korean Natural Farming, and involves “farming” captured forest microorganisms (most noticeably, fungi) with a bait of cooked grain. There are four stages. Making IMO #1 involves incubating cooked grain (mixed with sugar) perhaps with some duff from the forest floor. The lidded box is set in a forest, covered over with more duff, and left for a week. Once white fungal mycelia (and perhaps other colors of fungi) cover the surface of the grain, you have IMO #1. The box is brought back from the forest and further processed to produce a large pile of active life.

Mix IMO #1  with sugar 1:1 by weight in a crock, cover it with paper and keep at room temperature for a week. This is IMO #2. To make IMO #3, stir this material in water and mix with bran. Pile the damp material on the forest floor, cover with wet leaves, straw or cardboard and tarp if it’s rainy. The pile heats up and produces more white fungal growth. After about 5 days, make IMO #4. Add an equal volume of soil to the bran pile and mix in. After about a week the material is ready to use. IMO #4 can be spread directly on the beds at 5 gallons per 250 ft2, approximately every other year. Or it can be used as a foliar feed. It acts as a catalyst to grow stronger plants. Improvements to the soil can include better aggregate structure, and better release of nutrients.

Weed, insect and disease control come next in the book, necessary but not directly income-earning aspects of farming. Increasing crop health and vitality for the long term is of fundamental importance here. There is a sense in which pests can be useful: as indicators of an imbalance that the grower would do well to address.

Reducing the weed seed bank is a long-term improvement. Destroy weeds as they germinate, and do not bring up weed seed by tilling. Try not to import weed seed with brought-in materials. Since Bryan was able to stop tilling, galinsoga no longer pops up [envy!]. Crop rotation can help break weed cycles by altering the growing environment. Switch between cool weather and warm weather crops, soil-covering crops and vertical crops, and keep roots in the ground all the time.

Stale seed beds and shallow hoeing can kill weeds without tillage, and solarization can kill not only germinated seeds but ungerminated ones near the surface. Mulches can prevent weed seed germination. Good hoeing technique and tools can remove the weeds that still pop up.

Don’t over-react if problems arise. Monitor pests or diseased plants and count a sample. Determine if the pest numbers warrant your intervention. Also determine if it’s too late to save that crop. Learn if managing the crop differently next time might make it more resistant to pests or diseases. It might take a season or two for changes to pay off in terms of stronger crops. Carefully look for any improvement, as an indicator that your actions are steering things in the right direction.

Beneficial insects, rowcovers, insect netting, shadecloth, shelterbelts and other kinds of crop protection all help crops grow stronger. I learned that our friends, the Cotesia glomerata wasps that parasitize brassica caterpillars, and overwinter as pupal cocoons on the undersides of brassica leaves, will hatch out in spring on the very day the overwintered brassicas start to flower. The 20-50 day lifecycle needs brassica flowers, so don’t be in a hurry to cut down all your bolting greens! The flowers provide nectar for the adult wasps. The leaves, as we know, provide food for the caterpillars, which provide the host for the wasps to lay eggs in. The wasp larvae feed on the caterpillar until it dies, then pupate.

There’s an incredible National Geographic video of this cycle, showing parasitic wasp larvae swimming around inside a caterpillar, bursting out through its skin. The weirdest bit is that it is the dying caterpillar that spins the protective cocoons around the pupating larvae. And us who plant the brassicas that feed the caterpillars! Who is the farmer and who is farmed?

The next chapter is on organizing things to produce vegetables year round. Off-season growing takes more attention and understanding than growing the crops at the easiest time of year. And can bring higher prices and more appreciation. People do want to eat year-round! Protective structures can earn their keep. Tobacco Road Farm uses lots of low tunnels in their snowy winters. Snow cover is actually a benefit to low tunnels, holding the covers in place, and providing insulation. In our climate, I think hoophouses work better. Because our winter weather switches back and forth from cold and icy to warm and sunny, we would spend a lot of time ventilating low tunnels. Without snow cover, we suffer wind and radiation losses through the clear plastic on cold nights.

We need to harvest more frequently than growers in colder climates (not complaining!), and the stooping over, opening and closing of low tunnels gets tiresome. We appreciate walking around in our (no-till) hoophouse, where all the crops are visible at once. Different climates call for different solutions.  If you are working with winter low tunnels, read this book and learn how to customize a snow shovel for clearing snow from the tunnels, by rounding and smoothing the corners of the blade. And here are tips for charring sawdust to melt thicker snow. They use a pump to blast a slurry of charred sawdust, salt and molasses over the tunnels. Sounds like a fun winter activity!

Bryan points out how healthy, sturdy crops will have a longer shelf life after harvest, paying back the year-round attention to soil and environmental health. Here are tips on ergonomic harvesting of small crops at ground level (rest one elbow on your knee) and efficient harvesting (while cutting, decide where to make the next cut). The speed of decision-making can be the bottleneck in harvesting, so practice to speed your decision-making.

Why do we grow vegetables? To meet basic human needs for health and happiness; to provide healthful foods, with the potential for job satisfaction and happiness. Sometimes slogging through and finishing a project is the most efficient. Sometimes switching to a different plan is more efficient (or at least, effective). Efficiency includes having a plan and having the flexibility to change plans.

The Further Reading includes a list of twenty books, and I am honored to be among those 26 authors. There is only one other woman among the authors. Bargyla Rateaver is from Madagascar, and with her son Gylver Rateaver, she wrote The Organic Method Primer in 1993. Some reviewers and obituary writers refer to Bargyla as “he”. Farmers are not all of one gender (or of one color). Thanks Bryan, for including some of the diversity that exists.

At the beginning of this review I said it was not a “menu” book, but a “specific method” book. Then I found myself picking and choosing from the ideas Bryan presents. It really isn’t a fixed meal. There is something everyone will love in this accomplished work. You don’t have to add all the Special Sauces.

Potato pests and diseases

Potato pests and diseases

These potatoes were almost killed by frost two weeks previously, and have now recovered.
Photo Pam Dawling

This is part of a monthly series on growing potatoes, a dietary staple.

PART ONE: Planting potatoes (April)

PART TWO: Growing potatoes (May)

PART THREE: Potato pests and diseases (this one, June)

PART FOUR: Harvesting potatoes (July)

PART FIVE: Storing potatoes (August)

PART SIX: Planning to grow potatoes again (September)

I have a whole chapter about potatoes in Sustainable Market Farming, where most of this information can be found.

See Root Crops in June for info on digging up new potatoes, if you can’t wait for them to mature!

See The Potato Association of America, Commercial Potato Production in North America 2010 for lots of interesting info, including planting in hot weather. (But hurry up, you need to have enough growing days left in the season to get them to maturity.)

Organic Integrated Pest Management involves tackling pest problems one step at a time with ecologically-based practices, starting with actions to reduce the chances of the pest ever getting a grip on your crops. I recommend the ATTRA online publication Organic Integrated Pest Management. Each of the 22 pages is a poster, complete with good photos and concise clear info. Because nightshades have a lot of fungal, bacterial and viral diseases, it pays to take action to minimize the chance of diseases attacking your plants.

June-planted potatoes in early September
Photo Kathryn Simmons

Integrated Pest Management in Organic Field Crops Webinar from eOrganic

https://www.youtube.com/watch?v=nQXC8SElTMk

Biological IPM disease and pest reduction strategies for potatoes

  1. Cultivate strong crops and provide healthy soil, sufficient space, nutrients and water, suitable temperature, and soil pH.
  • Choose varieties that resist the pests and diseases you most expect. Improve the soil tilth, drainage and aeration. Chisel plow or broadfork to break hardpan, or grow deep-rooting cover crops ahead of your potatoes. Maximize air circulation around the plants. Choose a bright, breezy location (avoid frost pockets as they also collect dew), orient the rows parallel to prevailing winds and give the plants plenty of space.
  • Add compost and cover crops to build fertile soil to support strong plant growth and help increase the diversity of soil microorganisms, building naturally disease-suppressing soil. Use foliar sprays of seaweed extract, microbial inoculants or compost tea to boost general disease resistance. Consult ATTRA for compost tea Brew one part of compost to 5 parts water by volume for 14 days before spraying.
  • Practice crop rotation to reduce the chances of pests and diseases carrying over from one crop to the next. For potatoes, it’s best to rotate away from nightshade crops for at least three years. We don’t manage this ideal of one year in four. In our ten-year rotation, three of our ten years are nightshades (one paste tomatoes and peppers, two plantings of potatoes).
  • Practice good sanitation. Clear old crops promptly, so they don’t act as a breeding ground for pests or diseases. Avoid smoking, especially near nightshades, and have smokers wash their hands with soap or milk before working with potatoes. Tobacco can spread tobacco mosaic virus (TMV) to nightshade plants. Avoid working potato plants while the leaves are wet. Remove and destroy diseased plants, especially for late blight. Clean tools in between use in one field and another. When the harvest is finished, till the tops into the soil to speed decomposition, or remove and compost or burn them if growing on a small scale.
  • Remove nightshade weeds (e.g., horsenettle, jimsonweed and black nightshade), which can be alternate hosts for pests and diseases.
Potatoes, weeds and standing water. Don’t let this happen to you! Provide good drainage, remove weeds especially nightshade weeds.
Photo Bridget Aleshire
  • Prevent soil splash-back onto leaves, to reduce outbreaks of soil-borne diseases. Use drip irrigation rather than overhead sprinklers.
July photo of a mulched June-planted potato.
Photo Wren Vile
  1. Cover or protect the plants physically from the pests
    • mulches to stop soil-dwelling pests (CPB) moving up into your crops
    • netting or rowcover to protect from airborne pests (leaf hoppers, blister beetles)
  2. Provide habitat for natural enemies and other beneficial insects. Farmscaping with sunflowers, peas, vetch, buckwheat or small grains, to encourage ladybugs and lacewings, can make insect control unnecessary in a good year. Ground beetles and bats can consume surface and air attackers before you even need to look.
  3. Monitor your crops regularly at least once a week and identify any pests you see.
  4. Introduce natural enemies of the pest (bacteria, fungi, insect predators or parasites). Try biofungicides for use against some diseases. F-Stop, T-22G Biological Plant Protectant Granules or other forms of Trichoderma can control Rhizoctonia, Fusarium and Sclerotonia. Soil-Gard (Gliocladium virens) can work against Rhizoctonia. Bacillus subtilis works against Rhizoctonia, and Sclerotonia. Mycostop (Streptomyces griseoviridis) can be used against Phytophthora, Alternaria, 35% hydrogen peroxide diluted to a 0.5–1% foliar spray solution may help control early blight. 1% solution = 3.7 oz in 124.3 oz water to make one gallon (1 ml:33 ml). There are commercial products such as Oxidate that are based on hydrogen peroxide, which is corrosive and challenging to handle.
  5. Hand pick (or trap) and kill the pests if the pest population is above the action threshold. Many fruit and root crop plants can take 30% defoliation before suffering any loss of yield. Where the crop is the foliage, this may be too much, but people don’t east potato foliage!
  6. Use biological controls (often derived from natural enemies) if the damage is still economically significant after trying the earlier steps in the process, including Spinosad or Bt.
Colorado potato beetle on an eggplant leaf.
Photo Pam Dawling

Potato Pests

Potatoes can be attacked by more than 150 insect pests. But don’t despair! In each region there are only a few species that could cause unacceptable losses of yield or quality. These losses can result either directly from the insects or indirectly by transmission of diseases.

Colorado potato beetle is the most common pest that potato growers get to deal with. The pink blob-like larvae of this beetle can eat enormous amounts of potato leaves while growing into bigger pink blobs. Left alone they can kill a planting. Acceptable amounts of defoliation without causing loss of yield are surprisingly high: 50%–75% of the top leaves on a young 6″–8″ (15–20 cm) plant, 25% on a 12″–16″ (30–40 cm) plant, a mere 10% at the critical full bloom stage (when the tubers are sizing up), and up to 25% once full grown. As with many pests, having a few of them is not important — it’s all about the numbers. Action to control CPB is only needed if the number of adults or larvae is higher than 1.5 per plant or egg masses exceed one per ten plants.

Crop rotation is effective, because Colorado potato beetles overwinter as an adult in the soil and when they emerge they have to walk around searching for a potato plant. CPB can have 1-3 generations a year. Even where two or three generations are usual, a significant portion of the summer generation adults go directly into the soil and become dormant. Eggs are laid in clusters of 20 or more. They look like ladybug eggs but are a stronger orange color – don’t kill the wrong ones! The beetle can go from egg to adults in as few as 21 days. There are four larval instars, with 75% of the total foliage destruction caused by the final and fattest instar.

Colorado Potato beetle late stage larva or pupa.
Photo Pam Dawling

Mulching with hay or straw can prevent CPB finding your potato plants – we never find them on our summer planting. Our unmulched spring planting is a different matter. I scout that field once a week, counting adults and larvae on a hundred randomly selected plants. As soon as I see more than 50 adults or 150 large larvae or 400 small larvae per 100 plants, I unpack the sprayer. I do a spraying with Spinosad, a fermentation product of a soil bacterium. It kills insects by over-stimulating their nervous systems. Spinosad kills a wide range of helpful and harmful insects too, so spray in the early morning or late evening when bees are not flying. Shake the bottle well, and mix following the instructions. Clean and triple rinse the sprayer. Do not flush in the creek or pond. Repeat in 6 days, but only if needed. Usually one spraying is enough, although I continue weekly checks. In the South, there can be three generations of CPB each year, so stay vigilant.

Prior to using Spinosad, we used Bt. The version of Bt for CPB nowadays is Bacillus thuringiensis var. tenebrionis. The kurstaki strain (such as Crymax) generally available in small quantities previously is genetically modified, so we stopped using it, not wishing to be part of any support for GMOs.  Neem and Beauvaria bassiana can also kill CPB larvae.

Flaming when the potatoes are less than 8” (20 cm) tall, is another effective control measure for CPB. Choose a warm sunny day when the pests are at the top of the plants. Flaming can kill 90% of the CPB adults and 30% of the egg masses, according to Colorado Potato Beetle: Organic Control Options – ATTRA

Young eggplant struggling against lots of aphids.
Photo Pam Dawling

Insects with piercing-sucking mouthparts damage potatoes by physical injury to the leaves, sucking out phloem, injecting their toxic saliva and possibly transmitting diseases. While potatoes can grow new leaves, there is still damage to plant health. Direct injury by sap-feeding insects can kill the plant. Soil-dwelling insects have only minor effects on yield, generally, but can reduce tuber quality and storage life.

Aphid-transmitted viruses cause greater losses than all other insect-related damage together. There are at least 9 aphid-transmitted potato viruses. Aphids can be reduced by farmscaping, planting flowers which attract ladybugs, lacewings and other aphid-eating insects.

Clover flowers attract beneficial insects. Red clover in June.
Photo Pam Dawling

Potato leafhoppers are a bad problem in central and eastern North America. They overwinter on the Gulf Coast. In spring, flying adults are transported north on upper level airstreams. Yield loss can occur before visual symptoms are obvious. Leafhoppers can cause leaves to shrivel and die. The initial effects are reversible if leafhoppers are controlled before leaf tissue is destroyed (“hopperburn”). By reducing the green leaf area, hopperburn affects photosynthesis and growth. The most vulnerable stage is when the tubers are bulking up. Leafhoppers can also transmit diseases. Trichogramma wasps parasitize leafhopper eggs. Garlic with insecticidal soap, sprayed early in the morning, especially on the undersides of the leaves, can control hoppers.

Potato psyllid occurs in the western U.S. Damage to the roots and tubers is caused by feeding nymphs, which can cause psyllid yellows. The first symptoms of psyllid yellows include stunting, loss of green color, leaflet distortion, reddish discoloring of new leaves, and the appearance of aerial tubers. Early action can stop and even reverse the damage. Adults cause little to no damage underground.

Wireworms (click beetle larvae) can tunnel through the tubers. Wireworms can live for 1-3 years, so crop rotation is important. Avoid planting potatoes the first year after turning under pasture or lawn. If you expect to have wireworms, plant small whole seed potatoes rather than cut pieces. Cut slices of potato can be used to trap wireworms (dig up the trap pieces each day and kill the wireworms.

Cutworms can eat the leaves from the bottom of the plant up (the opposite approach from CPB larvae). Once the plants are fully grown, up to 75% loss of lower leaves is unimportant. At earlier stages, if any cutworm damage is seen, dig around the stem, find and kill the cutworms.

Blister beetles can cause trouble later in the season, skeletonizing leaves and spreading a wilt. They contain cantharadin, which can cause blisters on the skin of unwary workers. Blister beetles can be trapped in crops of chard or beets next to the potatoes. The beetles are easier to see and catch in the trap crops than in potato foliage. If there aren’t too many it may be worth putting up with them, as their larvae are carnivorous and eat grasshopper eggs.

The potato tuber moth damages both foliage and tubers during growth, but the biggest losses occur in storage. Larvae inside the potatoes can continue their development in storage, filling the tubers with frass and letting in decay organisms. When commercial infestations are high, the crop is not worth harvesting because of labor costs to cull out the infested tubers.

 Nematodes can be deterred by choosing appropriate preceding cover crops, or by applying 1-2 tons/ac (2240-4480 kg/ha) of crushed mustard seed meal to the soil before planting. This will also reduce early weeds and act as a fertilizer. 

Potato Diseases

Before a plant can become diseased, three conditions must exist: a susceptible host, a disease organism, and a suitable environment for the pathogen. The choice of the disease control method should be based on an accurate identification of the pathogen and the disease.

Late blight on a potato leaf. http://blogs.cornell.edu/livegpath/gallery/potatoes/late-blight/

Late Blight (Phytophthora infestans) is by far the worst disease to afflict potatoes. This is the disease that contributed to the famine in Ireland (caused by the profiteering of the English land-owners, who sold the barley and left the tenant farmers to subsist almost entirely on potatoes). The disease is caused by a species of a fungus-like oomycete or water mold (previously considered a fungus, now reclassified as protozoa) that blows in on the wind. It is worse in warm wet weather with cool nights. Late blight starts as “water-soaked” spots on the leaves. These expand into gray-black “scorched” areas, sometimes with a dotted white mold growth, especially on the underside of the leaves. Cut stems reveal a dark circle of infected tissue. The disease spreads rapidly, turning plants black, as if badly frosted, and can kill an entire planting in ten days unless stopped by hot dry weather.

The best defense is to always remove volunteer nightshades from your fields and compost or bury all crop debris. The disease spreads via cull piles, nightshade plants and petunias — it needs live plant material to survive. If you find volunteer potato plants popping up in early spring, it is best to pull them up! Spores survive winter in warmer climates and then blow north and uphill. Preventive action may be taken with sprays every five days of (toxic) copper products, hydrogen peroxide, Bacillus pumilus or Bacillus subtilis products.

If Late Blight occurs late enough in the season, you can save your crop by mowing off the foliage, raking it off and disposing of it, and leaving the field untouched for two weeks before harvesting whatever potatoes have grown. This prevents the spores getting into the soil and infecting the tubers. Disposing of large amounts of blighted foliage is no easy task. When I had to deal with Late Blight, back in the 70’s, we made a fire and gradually added more tops as the previous ones burned. This was a very smoky fire, polluting, and no doubt contributing to global warming. Digging a big hole and burying it all is probably better.

Early Blight (Alternaria solani) is a common fungal disease, which mostly affects stressed or older plants. It starts as small brown spots on the lower leaves, which conglomerate into brown blotches that are restricted by the leaf veins, and so they can be angular in shape. The lesions have a bullseye appearance – concentric circles with a yellow halo around each one. During warm humid conditions, the fungus steadily defoliates the plants, reducing yields. The disease is seed-borne, soil-borne and airborne, surviving on plant debris and nightshade weeds. Early blight (Alternaria solani) can appear late in the season, not just early, despite the name. The manifestation of blight symptoms can be minimized by growing strong healthy plants, supplying sufficient water, and spraying with compost teas. The beneficial fungus Trichoderma harzianum can give good results.

Black Scurf or Stem Canker fungus (Rhizoctonia solani) is worst in cold wet soils. Early in the season it can cause sprout death. On older plants, red-brown stem lesions develop into cankers, and the infection can spread to the tubers, which then become cracked and misshapen, and may have dead tissue at the stem end. There may be firm black sclerotia (small dried reproductive bodies) on the tuber. In future, get disease-free seed potatoes and wait for the soil to warm a bit before planting.

White Mold (Sclerotinia sclerotiorum) on the vines. If you want to prevent this in future, you could dust the seed pieces with the commercially available fungal antagonists Trichoderma viride and Trichoderma virens.

For a chart with about 30 potato diseases, see The Potato Association of America, Commercial Potato Production in North America 2010

A lady bug on a potato leaf, perhaps producing larvae to help control aphids.
Photo Kathryn Simmons

Root Crops in June

Early September photo of mulched June-planted potatoes.
Photo Kathryn Simmons

Root Crops to Plant in Central Virginia in June

Potatoes: Yes, it is OK to plant potatoes in June, up until late June. Count back from your first frost date the 80-100 days or whatever your chosen variety needs to mature. See my post on planting potatoes. We buy our seed potatoes for the June planting in April, before local suppliers sell out of spring stocks. We store them in our walk-in cooler until two weeks before the planting date. I recommend some special techniques for summer potato planting. See the Other Root Crops Tasks section below for more details. An advantage of summer planting is that the harvested crop need only be stored from October or November, not over the hotter months.

Sweet potatoes: It’s still OK to plant sweet potatoes in June in central Virginia, and if you live in a colder climate, you probably wouldn’t even try to plant in May. It is best if the soil temperature is 65°F (18°C) for four consecutive days before planting.  See my post on sweet potato planting

Carrots: We direct sow our seventh bed of carrots in mid-June. It can be hot and the challenge is to keep the soil damp. Unlike some other crops (lettuce and spinach come to mind), carrot seed will germinate just fine at high temperatures. Shadecloth can help keep the soil damp, or you can just water a lot. You won’t need to do daily watering for long: maybe only 4 days. See Root Crops in May.

We only sow in June and July if we really need carrots, as hot weather impairs the flavor. Our hope is always that we will have grown enough between February and May to last till late October, and have bags in storage in the walk-in cooler. Sow carrots whenever the soil is below 95°F (35°C), so long as you can keep the surface damp. In summer we flame carrots on day 4 after sowing, because we have found that carrots can emerge on day 5 in summer temperatures, despite longer times given in the charts. See Root Crops in May for more about sowing and growing carrots, including pre-emergence flame weeding.

See the Special Topic below for more on growing carrots.

Warmer climates with later frost dates than central Virginia: you may still be able to plant crops we gave up on in May.

Colder climates: you may need to sow rutabagas, which we don’t need to do till July.

Root Crops to Harvest in Central Virginia in June

Cylindra Beets.
Credit Southern Exposure Seed Exchange

Beets: We like Cylindra best (55 days to maturity, OP). Detroit Crimson Globe is said to maintain better flavor in hot weather than most others, which can develop off-flavors. Remember as you harvest beets to check the leaves, as possible cooking greens too.

Beet leaf with Cercospora leaf spot.
Photo Purdue vegcropshotline.org

Later in the summer ours develop spotty holes from Cercospora Leaf Spot, and become unappetizing, but in early June they are usually fine. We like to clear all our spring beets by the end of June.

Store beets at 32°F (0°C) and 95% humidity. Trimmed beets keep well in perforated plastic bags under refrigeration. We have “rediscovered” stored bagged beets at the back of the refrigerator 9 months or so later and they were in fine condition.

There are also non-electric storage methods for roots, but these mostly rely on cool soil and cool air, so I’ll write about those when we get to fall. If you have a root cellar with a good temperature, you can use that. I have a chapter on root cellars in Sustainable Market Farming.

Carrots: Our second carrots (sown in late February) and third (sown in mid-March) will be ready to harvest in June. Possibly also our fourth sowing (late March), by the end of June. Don’t leave them in the ground too long, or they will get fibrous and woody. No fun!

Fennel bulbs: if you planted those in spring, they will be ready in June in central Virginia. If you didn’t grow this, consider it for fall, when it is easier to grow it without danger of it bolting. I wrote about fennel as a hoophouse crop in The Year-Round Hoophouse.

Kohlrabi: In our zone 7 climate, kohlrabi, like other brassicas, can be grown in spring or fall. So you can buy seed now and plan for kohlrabi in October, November, or into the winter if you store it. In spring we harvest kohlrabi from May 10 to June 30, when they reach 2-3” (5-7.5 cm) in diameter (or even up to softball size). The base of the globe can be quite fibrous, so cut either the wiry root just below the soil surface, or cut higher, leaving a small disc of the globe behind, attached to the root. We definitely need to dig all our spring kohlrabi by the end of June at the latest, or they get too woody. Unlike carrots and turnips, fennel and kohlrabi can successfully be transplanted.

Potato harvest.
Photo by Nina Gentle

Potatoes: In mid-June we can start harvesting spring-planted potatoes as delicious “new” potatoes. Check under a plant to see how big the potatoes are. If they are big enough and you aren’t worried about reducing later final yields by starting early, go ahead and dig some. It doesn’t matter that the tops haven’t died. These new potatoes will have shreds of thin skin, not the firm skins needed for potatoes to be storable, so just dig them as you need them. If this is your first year growing potatoes, you will be amazed at how good they taste boiled with a sprig of mint. So much tastier than store-bought!

Turnips:  They are among the fastest growing crops other than leafy greens. We harvest our spring turnips gradually, pulling the biggest and letting the rest grow bigger. By the end of June, though, we need to have them all up and if we have plenty, we store some in perforated plastic bags in the walk-in cooler, until mid-July. Turnips will keep for about 4 months at temperatures close to freezing and humidity of 90-95%. Higher humidity will make them rot.

Early Purple Top Milan turnip in late May.
Photo Pam Dawling

Other Root Crops Tasks in Central Virginia in June: Summer Potatoes

In early June, in preparation for mid-June planting, we chit (pre-sprout) our seed potatoes for two weeks in trays in the light. Unlike chitting in February and march, the potatoes don’t need supplemental heat at this time of year. The method is the same as I described in my post Planting Potatoes. Let all the sprouts grow. For warm-weather planting, one sprout per seed piece is usually sufficient – the chance of frost is over, and “spare” shoots are not needed. Tubers with many sprouts can be cut into many seed pieces, which can save money. See the Planting Potatoes post for details on Cutting Potato Seed Pieces.

In warm conditions, deeper planting, hilling and thick organic mulches all help keep the plants cooler, as does irrigation. To help keep the soil cool while the potatoes are growing through the heat of July, August and September, we mulch with spoiled hay. (Straw would be nice, but this is not a grain-growing area). We bale our hay in the big round bales, and we have almost a quarter acre of summer potatoes to cover, so it is by far easier for us to unroll the bales before the potato shoots emerge from the soil. To lay the mulch by hand around the potato plants after they come up would take way too much work on our scale. Home gardeners may use loose mulch and tuck it in around the plants later.

So, in order to mulch the day after planting, we cover the seed pieces with soil, using the tractor and the hiller. (When we used our BCS tiller for this, we simply tilled between the rows, which leveled the field and covered the potatoes well enough). Then we hill, and unroll round bales of spoiled hay immediately, or the next day. Potatoes emerge quickly in warm weather! Hilling is tricky without any visible signs of where the potato pieces are. We have sometimes used stakes and ropes to mark the rows, or else flags at the ends of the rows, and crossed fingers as we drive the tractor and ridger down the field.

Unrolling hay bales is close to an Olympic team sport! We line up the bales (using a tractor and hay spike or forks) shoulder to shoulder at the uphill end of the patch. Our land is almost flat, but even a slight slope makes a noticeable difference when pushing a hay bale, so do start at the top end! Next we study the pattern of the grass stems in the ends of the bale, and if needed twizzle it round 180 degrees on the ground, so that it will unroll itself when pushed. We cut and remove the twine, then two or three people start it rolling. Once it’s going, each bale has two people unrolling it, and eventually it gets small enough for one person to handle and the other can go back to the top and help start another bale. We try not to walk on the hills and we try to lay out the hay like wall-to-wall carpeting, without gaps.

Newly mulched potato patch in June.
Photo Pam Dawling

About 16 days after planting, in late June, we do a walk-through, one person per row evening out the mulch, and freeing trapped potato shoots. Everywhere we expect to see a potato but don’t, we part the mulch carefully, seeking pale flattened shoot. If we find one, we rearrange the mulch a little, so that the shoot is exposed to the light, but the soil is not. It’s not necessary to expose the whole shoot – even a little bit of stem is enough for the plant to reorient itself and be fine.

Later in the season we’ll need to weed the potatoes. I haven’t been mentioning it, but weeding is important for all crops, especially direct-seeded crops.

Special Root Crop Topic for June in Central Virginia: Carrot Types

I wrote quite a bit about sowing carrots, in the Root Crops in May blog post

These days there are many fancy colored carrots, but my preferences all lie with bright orange carrots, rich in beta carotene. We have tried growing a few white, yellow and purple varieties, but frankly I found them all very disappointing, as far as flavor and succulence. They tended to be scrawny! All carrots sweeten up when days are warm and nights cool.

Carrots come in five different carrot types based on their shape and size. The factors influencing your choice will be soil type, climate, market, and harvest time and method.

  1. Danvers are a long, thick-rooted cylindrical shape tapering to a point. They often have a yellowish core. The leaves and taproot are both longer than Chantenay types. They are suited to high production of bulk carrots and widely used in processing. They store well. They are more tolerant to poor soil, but grow best in deep, sandy loam. Making raised beds helps.

Varieties: Danvers (OP), Healthmaster (F1), Danvers Half Long (OP), Danvers 126 (OP)
Season: spring to fall. Summer in cool climates
Days to Maturity: 70-80 in spring, 80-110 in the fall

In central Virginia, zone 7, on a sandy clay loam, we grow Danvers 126, a sturdy open pollinated variety.

Danvers Half Long carrot
Photo Southern Exposure Seed Exchange
  1. Nantes are medium-length, straight, cylindrical roots 5-7” (13-17 cm) long with blunt tips and sparse foliage. A very quick growing variety. Nantes types have sweet, juicy, tender, crisp, almost red flesh; but only limited storage potential, and they are somewhat brittle. They contain few terpenoids, the volatile flavor compounds we think of as “carroty”. When poorly grown, they can be watery and bland. Nantes do best inloose, sandy soil or raised beds enriched with organic matter

Varieties: Early Nantes (OP), Scarlet Nantes (F1), Bolero (F1), Mokum (F1), Napoli (F1)
Season: spring to fall; summer if not too hot
Days to Maturity: 55-70 in spring, 60-75 in fall

We have grown the 75-day Bolero, a high-yielding carrot that stays sweet even in storage. 6-7” (15-18cm) long, with a 1 ½” (4cm) crown. It looks a bit prettier, and has slightly better flavor than Danvers, but ultimately we decided the extra cost of the seed was not worth it to us. The resistance to Alternaria or Cercospora found in Bolero has been important for our fall crop.

Scarlet Nantes carrot.
Photo Southern Exposure Seed Exchange
  1. Imperator –Most commercial growers produce this type. They are similar looking to Danvers, but bigger: longer, thicker in width, with stocky shoulders and strong fast-growing tops. They store very well. They perform best in deeply worked sandy loam soil. In rougher soils, they develop a slightly fibrous texture. Imperator types contain more terpenoids, and can be prone to bitterness if something goes wrong. Many hybrid varieties are a cross between Nantes and Imperator types.

Varieties: Sugarsnax (F1), Autumn King (OP)
Season: spring to summer in cool climates, or summer to fall
Days to Maturity: 55-100 in spring, 80-110 in fall

I have grown Autumn king in England and it was a very reliable variety.

Imperator carrots.
Photo Southern Exposure Seed Exchange
  1. Chantenay:short and broad conical roots with rounded tips, 6-7” (15-17 cm) long. Very vigorous top growth. Rich, sweet flavor. Chantenay store extremely well. They are the best type to plant in shallow, rocky or heavy clay soil due to their shape. Of course they also do well in better soils! These are a great choice for those gardening in containers. It is important to harvest at the appropriate length because they become woody and poorly flavored if harvested too big.
Red-Core Chantenay carrot.
Photo Southern Exposure Seed Exchange

Varieties: Red Cored Chantenay (OP), Kuttiger (white, OP), Kuroda (OP) Hercules (F1), Carson (F1)
Season: spring to early summer, midsummer to late fall
Days to Maturity: 55-70 in spring; 70-110 in fall

I have grown Red Cored Chantenay (65 days), a blocky variety with a blunt tip, 5″ (13 cm) long and 2″ (5 cm) at the shoulder. It resists splitting. The flavor of Chantenay types has been described as “parsley-like”. Kuroda types have a drier, creamier flavor. They are tolerant to Alternaria.

Heavy yield of Oxheart carrots.
Photo Southern Exposure Seed Exchange

In the past, before the soil here had been improved, we had to grow shorter carrots, as the long ones would break in the tight soil. Most of the varieties recommended for clay soils are small, as well as short. Nearby at Southern Exposure Seed Exchange, they have had astounding success with Oxheart (90 days, OP) a large, squat, chubby Chantenay type, with shoulders reaching 5″ (13 cm) across and 3-4″ (7-10 cm) long with a full carrot flavor.

  1. Miniature: round, cylindrical or tapered roots less than 5” (13 cm) long; crisp texture and frequently quite sweet This grouping includes carrot varieties that are shaped like radishes and miniature regular-carrot shaped ones. They work extremely well in containers due to their short taproot; They will grow in any fertile soil that drains well They have only limited storage potential.

Varieties: Thumbelina (OP), Little Finger (OP), Parmex (OP), Atlas (OP), Babette (OP), Romeo (OP), Paris Market (OP).
Season: spring to early summer, late summer to fall
Days to Maturity: 50-60 in spring, 60-70 in fall

Atlas carrots.
Photo Johnny’s Selected Seeds

Johnny’s has a pictorial comparison of some varieties on their website, under Growers’ Library/Vegetables at for maincrop and storage carrot varieties, the tiny round Atlas, Romance, Hercules, Bolero, Nectar and the long slender Sugarsnax; and  for early varieties, small Adelaide, Yaya, Mokum and Napoli.

Everything You Need to Know About Garlic; Money and More

 

Softneck garlic ready to harvest
Photo Pam Dawling

We started harvesting our hardneck garlic on May 26 this year. One of the earliest harvests we have on record.

I’ve written lots on garlic in this blog, it’s one of the most sought-out topics. To cut to the chase, here’s my Garlic Recap.

Many of these are posts in my Alliums for the Month Series:

Harvesting garlic scapes
Photo Wren Vile

For a second opinion, see Margaret Roach (who grows in Massachusetts) in A Way to Garden

Music garlic cut open showing gaps around stem – a sign of maturity.
Photo Southern Exposure Seed Exchange

Of the many other posts I’ve written on garlic, that are not mentioned already, starting with harvest and moving round the calendar, there are:

Harvest

Garlic Harvest step by Step

Harvesting Garlic

Garlic Harvest

Garlic harvest, Intercropping, Summer lettuce,

Garlic harvest finished, fall crop planning, tomato bug heads-up

Garlic hanging in netting to dry and cure.
Photo Marilyn Rayne Squier

Drying and Curing, Snipping, Sorting and Storing

Garlic drying and curing methods

Snipping, Sorting and Storing Garlic 

Planting garlic

Sustainable Farming Practices slideshow, garlic planting, annual crop review

Garlic Planting and Freeing Trapped Shoots

Winter radishes, planting garlic.

Garlic scallions in March
Photo Pam Dawling

Garlic scallions

Harbinger weeds of spring, and early garlic scallions

Garlic scapes

Garlic scapes! Three weeks to bulb harvest!

Too much rain! But garlic scapes to cheer us up.

Garlic scapes

Garlic scapes, upcoming events, hoophouse seed crops

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My DONATE button

I’ve added a donate button, for those who’d like to use it (via PayPal or credit card). We’re all staying home, not going to conferences or fairs. This is reducing my opportunities to collect speaker fees or sell books face to face.

More people are reading my blog (thank you!). There are thousands of new or returning gardeners across the country, aiming to get fresh air and exercise while usefully putting their time into providing food for their households. There are experienced professional growers trying hard to make their farming more efficient, and pivot to find ways to still earn a living and not lose the farm, due to loss of markets.

I put a lot of energy into providing useful info and practical details, and so if you are finding my posts helpful, and you can afford to, please consider clicking the pay-what-you-can button.

Together we’ll get through this difficult time and reach better days again.

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Birth of Assassin Bugs

Debbie Roos, an Agricultural Extension Agent at Chatham County Center, North Carolina Cooperative Extension and the founder of www.growingsmallfarms.org is a wonderful photographer,. She recently reposted this.

A couple of years ago I posted a series of photos on my Growing Small Farms website showing assassin bug nymphs emerging from their eggs. It was an amazing thing to witness and not something you see every day. Folks really enjoyed seeing the photos back then and since it’s spring and time for more to emerge I thought it would be fun to share the photos again now that so many people are spending so much time at home!

Adult wheel bug feeding on a Japanese beetle. Photo by Debbie Roos. Click here to visit NC Cooperative Extension’s Growing Small Farms website to view the photos.

Be on the lookout for these egg clusters on your property and you may even get lucky and witness the birth of an assassin!

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Quick-Growing Vegetable Crops

Steve Albert has an informative website, Harvest to Table, and this post on quick-growing vegetables includes some warm weather crops like bush green beans and sweet corn. It includes names of fast-maturing varieties.

I wrote Fast Growing Vegetables in March, focusing on early spring crops. If you are still racing to catch up, or in need of more crops that yield quickly, see Harvest to Table.

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How to Fight Hornworms

On the Mother Earth News blog, my post How to Fight Hornworms has been very popular, and has led me to make an article for the Mother Earth Gardener magazine

This magazine is “a quarterly publication committed to giving you in-depth expertise to bolster your organic garden each and every season. Roll up your sleeves and learn soil-boosting strategies, permaculture practices, and more! Formerly known as Heirloom Gardener.”

Tobacco hornworm on tomato leaf
Photo Pam Dawling


16 things I know about growing tomatoes

From Margaret Roach at A WAY TO GARDEN

Margaret writes about home-grown seedlings, finding flavor, choosing between hybrids and open-pollinated varieties, saving seed, good tomato-hygiene, monitoring for pests and diseases, pruning, staking or otherwise supporting the plants, and dealing with the weather.

Jubilee tomato in our hoophouse.
Photo Pam Dawling

 

Planting Sweet Potatoes

Fresh sweet potato slips for sale from Southern Exposure Seed Exchange.
Photo Pam Dawling

Are you thinking about crops to grow that will feed a crowd next winter? Sweet potatoes are an easy crop to grow, provided your climate gives enough warm days. They store very well at room temperature, for a long time. In mid-late May, we are still eating sweet potatoes we grew last year, and they are delicious! Well grown and cured, sweet potatoes reach their peak in flavor during January and February. One baked sweet potato of 114gm (4 oz) has 185% the RDA of vitamin A, 28% the RDA of Vitamin C, 100% of vitamin E, lots of anti-oxidants, and 160 calories, none from fat.

Order some slips online and get the ground ready. You can order from Southern Exposure Seed Exchange 11 varieties, all organic, in bundles of 6–100. For more varieties but smaller orders, go to Sand Hill Preservation Center, Iowa. Heirlooms, 225 Varieties, all Organic. Some limits on how many you can buy. Another supplier I recommend is the Steele Plant Co, 10 varieties (not Organic) of slips in small (12) and large (500) quantities, good prices, great service. Slips are young shoots with stem, leaves and, usually, some roots. Sweet potatoes are not grown from seed or from chunks of potato.

I have known people grow sweet potatoes in hoophouses if their climate isn’t warm enough outdoors. This can fit with winter use of the hoophouse for greens and roots. My book Sustainable Market Farming contains a whole chapter on growing this crop, including growing your own slips, but it’s too late to start that this year.

Sweet potatoes fit easily into the crop schedule. Planting out comes later than most spring crops. It’s late enough to precede them with a mature cover crop mix (including legumes to the flowering stage), providing all the nitrogen needed. Or add an organic fertilizer this year and plan ahead for next year. Sweet potatoes do not need lots of organic matter, or high fertility levels. Fitting sweet potatoes into a rotation is easy because it is unlikely that you are growing anything else in that family. As with other crops, a three-year gap (or more) before planting sweet potatoes in the same beds helps control disease.

Modern varieties of sweet potatoes grow to a good size in as little as 90 days, so they are not just for the South! The further north you are, the longer the daylight at midsummer and the more photosynthesizing the plants can do.

Sweet potatoes thrive in hot weather and are fairly drought-tolerant. After vining they need little care during the summer (apart from irrigation) until harvest. Their extensive vines smother most weeds, and they have few pest or disease issues. Most of the labor is the harvest in early October, in-between most other intensive harvests of summer and fall crops. I’ll never complain about a crop which has most of the work be the harvest!

Understanding sweet potatoes

 Sweet potatoes are tuberous roots (Ipomoea batatas), related to morning glory, in the genus Ipomoea. Sweet potatoes or sweetpotatoes are native to the tropical regions in central and south America. The root is long and tapered, with a smooth skin, and color ranging from orange, yellow, beige, white, red, pink, violet and purple. Sweet potato varieties with white or pale yellow flesh are less sweet and moist than those with orange, pink or red flesh. The young leaves and shoots are sometimes eaten as greens. Hot weather greens are hard to find!

Sweetpotatoes are not yams, even though they’re often called yams! True yams are a tropical species of tuber (genus Dioscorea). They come from Africa and the Caribbean. Some are huge! They have rough and scaly skin. The flavor is starchy, and usually not very sweet (more like regular potatoes). Sweet potatoes will not even cross with yams.

Sweet potatoes are sometimes mistakenly thought to be a type of potato but they do not belong to the nightshade family, Solanaceae. Sweet potatoes are only distant cousins of the nightshade “Irish” (more accurately Peruvian) potatoes (Solanum tuberosum). Unlike Peruvian potatoes, which have the annual sequence of vegetative growth, flowering and dying back, sweet potato plants continue growing as long as the weather is warm enough. They are frost-tender herbaceous perennials.

A well-established young Georgia Jet sweet potato plant.
Photo Bridget Aleshire

Read more

 I have a Sweet Potato slideshow.

And I have written a lot of other posts on sweet potatoes (mostly about propagating our own slips, or about harvesting). Very little on actually growing them all summer. My posts include:

Starting Sweet Potato Slips

Sweet Potato Propagation and Yields

Transplanting Sweet Potatoes (biodegradable plastic; deterring deer)

Harvesting Sweet Potatoes (2016); Sweet Potato Harvest (2015) and again (2015) and earlier (2014) and in 2013, 2012

What Makes Sweet Potatoes Sprout (during storage)

I also have a blog post for Mother Earth News Organic Gardening blog, about growing sweet potatoes. And I have several articles in Growing for Market, which you can access online if you have a Full Subscription.

The vines of sweet potatoes start running after the roots have made good growth
Photo Bridget Aleshire

When to plant sweet potatoes

Figure out your ideal planting date. Planting is usually done about 2 weeks after the last frost. You need settled warm weather. Heat is vital. The soil temperature should reach at least 65˚F (18˚C) at 4” (10 cm) deep on 4 consecutive days—don’t rush into planting early. Plants set out too early will struggle with skin fungi, and produce uneven yields. Their growth will be stunted. Forget about climate zones—those are about winter-hardiness of perennials. Sweet potato growing is all about warmth and light. Your sweet potato plants can remain ignorant about your winter cold!

We plant May 10–20, between pepper, okra and watermelon transplanting dates. It takes 7–8 weeks to grow your own slips using our method, so buy slips for this year and learn how to save seed stock when you harvest, to grow your own slips next year.

Planning aheadhow many to plant

Decide how much space you want to plant, or how many pounds (tons?) you want to grow. One slip will produce a cluster of 4–10 roots, each weighing 3–17 oz (80–500 g). The yield range is 2.5–6.8 lbs (1–3kg) per plant, 276–805 lbs/1,000 ft² (14–40 kg/10 m²), or 6–17.5 tons/ac

The in-row planting space is 6–18” (wide spacing gives more jumbo roots). We do 15″ (38 cm) as we like to get some jumbos. If unsure, try 12” (30 cm). Climate, spacing, and the length of the growing season all affect yields.

The space between the rows could be 32–48” (0.8–1.2m). Calculate how many slips you’ll need and add 5–10%. For an acre you’ll need around 15,000.

Newly planted sweet potato slips with a motion sensor sprinkler to keep deer away. the wilting of newly-planted slips is common. Don’t despair!
Photo Pam Dawling

Sweetpotato crop requirements

 Sweet potatoes prefer loose, well-drained soil with pH of 5.8–6.2. They will tolerate pH from 4.5–7.5. Enough potassium (K) is important for drought-resistance, but too much K makes them taste bitter. Sweet potatoes do not benefit from high nitrogen (N). They can get plenty from high-biomass cover crops, organic mulch, and soil life.

Once they are established, sweet potatoes are fairly drought-tolerant. Critical times to maintain sufficient moisture are after transplanting and for at least the first 20–40 days while the roots are developing.

Tips to increase sweet potato yields

Compacted, heavy, lumpy soils can result in misshapen, undersized tubers. If you have clay soil or drainage problems, work in lots of compost and make raised beds or ridges 8”–12” (20–30 cm) high. Ridges help heat up the soil and reduce flood damage.

Black plastic or silage tarps set out 3 weeks before planting warm the soil considerably and increase the growth rate. In colder climates, plant under low tunnels of clear plastic. Ventilate in hot weather.

If it’s too cold to plant out your slips when they arrive, keep them indoors, with water covering the roots (remove any newspaper or other packing material). If you are planting in hot dry weather, water the soil first, and keep the roots enclosed in damp or wet compost as you plant.

We like to do two plantings a week apart, using the older slips first, and then do a third session to replace any casualties.

 

Young sweet potato plants with drip tape and ripped plastic mulch.
Photo Pam Dawling

Planting out sweet potato slips

 Prepare your beds or ridges. Get ready with your irrigation system. If you are covering the beds with biodegradable plastic mulch lay it out just before you will plant. Set out stakes and ropes to mark where the rows will be planted, and gather a measuring stick, trowel and watering can.

To grow the biggest roots, plant the slip vertically, which steers the plants to develop roots only from one node. To grow average size roots but many of them, plant slips horizontally 2–3” (5–7 cm) deep, encouraging tubers to develop at several nodes. Ideally, have 3–5 leaf nodes underground and only the tips above the ground—this gives the plants a second chance if a late frost strikes. Many growers have success with slips with few or no roots, but we like a good root system.

If you are using drip irrigation, run it while you plant. If the emitter spacing matches your plant spacing, plant in the damp spots without measuring. Otherwise, use a measuring stick or a double hand-span to get the plants evenly spaced and not waste plants or land, by diverging from your planned spacing. If you have driptape under mulch, feel for where the tape is, and avoid stabbing it with your trowel.

Firm the soil around each plant, so that it is not left sitting in an air pocket, unable to reach water.

If not using drip irrigation, stop every few plants and water from a watering can. Err on the side of too much water on planting day. Keep newly transplanted slips well-watered.

If it turns cold or windy soon after you transplant, you could use rowcover to protect the plants.

This motion sensor sprinkler has been working well to keep deer out of the sweet potato patch.
Photo Wren Vile

Sweet potato development

I usually reckon on the first month after planting being focused on root growth, the next month on vines and the rest on roots. Regardless of how early in the season you plant them out, they will not make flowers earlier, or start making tubers sooner. Both flower and tuber initiation are triggered by day length. Each variety has its own internal clock. Most varieties take 90–110 days from planting out to reach a good size, if the weather is warm enough.

The first month or so after transplanting is the root development stage. Roots can go 8’ (2.4 m) deep in 40 days. Don’t be alarmed at the lack of above-ground action. Give 1” (2.5 cm) of water per week, and cultivate to remove weeds. The second month or so is the vine growth stage. The roots begin to store starch and sugar close to the stem base. Cultivate until the vines cover the ground, after which very little weeding will be needed.

During the last month of growth for that variety (3rd or 4th month), the potatoes develop. Make sure you dig them up before the soil temperature gets down to 55˚F (13˚C) –the week of the average first fall frost is about right.

There are some pest mammals and insects, afflictions and diseases to watch out for, but usually sweetpotatoes will grow relatively untroubled until harvest time. Do watch out for deer, rabbits, and other rodents, or anything that appears to be reducing the leaf cover substantially. I’ll write more about these issues in a few weeks.

For more info, see ATTRA Sweet Potato: Organic production

North Carolina State University, Pests of Sweetpotato
North Carolina State University Diseases of Sweetpotatoes.

Book Review: The Earth in Her Hands, by Jennifer Jewell

Book Review: The Earth in Her Hands: 75 Extraordinary Women Working in the World of Plants, by Jennifer Jewell, Timber Press, 2020. 312 pages, full color photos throughout, hardback, $35.

The Earth in Her Hands is a beautiful book: a book to browse, a book to share with friends, a book that will leave you feeling you are with friends, even when you browse alone, a book to come back to often. By turns encouraging and comforting, as well as validating, reinforcing and supporting the value of our work caring for plants and their associated people.

Jennifer Jewell is the host of the radio program and podcast Cultivating Place, produced at an NPR station in Northern California; the writer of many gardening articles, and an advocate for gardening. Here she has assembled a four-page spread on each of 75 women.

Over 40 of the contributors describe themselves as writers or educators, and 24 as gardeners or farmers. I expect the total is higher, and that many contributors are excellent home gardeners, but didn’t mention it. The next biggest category is the 20 women who work as designers or architects of landscapes, parks or gardens. Overlapping these designers of spaces is the group of 8 floral designers.  This group is followed by the 15 who are some kind of public or school garden manager, director or administrator. Around a dozen (and I imagine more) are workers and advocates for social and environmental justice. There’s a group of about 25 who describe themselves as nurserywomen, horticulturists, plantswomen, botanists, plant hunters and native plant experts. Over a dozen are scientists and advocates in the field. A small group are plant breeders, seed farmers and seed scientists. And finally there are about ten garden, landscape or plant photographers and artists. I was disappointed there aren’t more vegetable growers, but I know writers write about what they know best.

One of Jennifer Jewell’s missions has been to Decolonize the Garden, to get away from images of middle-aged middle-class white people, working in the US with plants imported from Europe; and to do this without appropriating other people’s culture. Some of the women profiled address this issue directly. The women presented are mostly from the English-speaking countries of the world, but not only; majority white, but diverse in ethnicity, socioeconomic and religious backgrounds, sexual orientation and age. Each woman concludes her interview with a short list of one to four other inspiring women, either women who preceded them, or upcoming women more of us will want to know about. Some are very personal choices (family members), some are well-known; sometimes there are details, sometimes not.

Jennifer Jewell
Photo Workman Publishing

Some of the women are world famous in the growers’ world, like Vandana Shiva, Elaine Ingham, Jamaica Kincaid, Leah Penniman, Margaret Roach and Renee Shepherd. Some are famous Virginians, such as Ira Wallace from Southern Exposure Seed Exchange, Beth Tuttle president and CEO of the American Horticultural Society, Claudia West the landscape designer in Arlington, and Peggy Cornett at Monticello. Others we meet for our first time.

Each profile starts with Her Work, Her Landscape (or Her Plant), and Her Plant Journey.

Here are some of the gems I picked out from this book:

“Fear is a great motivator, and there’s no magic. Get up early and really work hard, show up on time, be nice, don’t overcharge, get a client and look after them. Be enthusiastic. You have to be knowledgeable—I’ve given myself a challenging education—I am open to other people’s thoughts, and I ask questions. I remain deeply grateful for all the people who have generously shared their knowledge and allowed me to learn from them. I try to repay this generosity every chance I get.” (Jinny Blom)

There are “plant people and there are garden people. Plant people focus on individual plants and collecting, garden people focus on the whole experience and space creation. . . I get obsessed with plants, but I don’t abide a plant that isn’t doing its job well in the garden.” (Flora Grubb)

“You may not like living with us now, but conservationists make great ancestors.” (Jean Siddall)

“One [of the three cooperatively determined goals at Soul Fire Farm]: grow 80,000 pounds of food intensively on two acres of land using low-till methods, sequestering 2400 pounds of carbon, growing over a dozen African-indigenous heritage crops, and demonstrating several African-indigenous sustainable farming practices. Two: train eighty-plus new farmer-activists of color through our Black and Latinx Farmers Immersion and its apprenticeship program, and mentor eighty-plus BLFI alumni. Three: train and inspire 250-plus youth of color through our food-justice empowerment program and immersion.” (Leah Penniman and Soul Fire Farm)

“Growing up, when cheap eggs were still more interesting to most people than free-range eggs, my mother . . . believed passionately that chickens have a right to run free and should be allowed to do so. How is it possible that we have people in our society without access to healthful food and green space? Even more enraging to me is that we are producing food that won’t ensure our long term health on this planet. How is it possible that we don’t care more about future generations than we do about producing too much cheap food poorly now?” (Alys Fowler)

“I recently heard form Sarah Milligan Toffler, director of the Atlanta Children &Nature Network, that children in the United States spend less time outdoors than prisoners. That took my breath away and puts fear into my heart. Public gardens are one antidote to that. They are a safe place to get kids into nature. Once there, being there, learning there, loving and caring about nature—they are inoculated for life!” (Mary Pat Matheson)

“Her diverse forty-member team at Studio-MLA includes landscape architects, urban designers, community advocates, botanists, ecologists, and technical experts, with a purposeful 50:50 men-to-women ratio from different ethnic and cultural backgrounds.” (Mia Lehrer). (Hopefully by now they have even gone beyond the binary gender classification.)

“When I first started attending conferences and meeting with growers, I would often be the only woman in a group meeting with a seed producer. Where others were mostly concerned with shipping and packing capacity, I was asking to compare varieties for flavor. Fortunately, that is changing now, as consumers are looking for more tasty produce.” (Renee Shepherd, owner of Renee’s Garden seed business).

I sighed to read that Jekka McVicar has been the only woman chair of the judging of the great floral pavilion at the Chelsea Flower Show (up to 2018). She has won 62 RHS gold medals since she started contributing to their displays and gardens in 1993. She was the only certified organic grower at the Chelsea Show, and she used the platform to “make a call for more insect-friendly gardening.”

I was somewhat cheered to read that Julie Kierstead Nelson benefitted in the late 80’s, from a class-action lawsuit against the US Forest Service for discriminating against women, and several congressional acts, including the Clean Water Act and the Endangered Species Act. The convergence of these forces helped her get the job she was seeking.

“As long as we keep topping off architects’ buildings with green roofs, we’re fiddling while Rome burns. We’re seven billion people now—we have to really figure out how to build cities, not just buildings.” “Great landscape design can moderate extreme heat, recycle water, reduce energy use, lower carbon emissions, and attract people to urban areas.” (Martha Schwartz)

The mandate for Sunset magazine in the Southwest “to not promote thirsty plants, potentially invasive plants, or plants with high pest problems,” (Kathleen Brenzel, the editor).

Claudia [West] believes that cultivated plantings of all kinds “must be beautiful, inspire, have emotional content, and provide high ecological value and function. They must feed and provide habitat for wildlife, clean our air, soak up and purify polluted stormwater runoff, sequester carbon, treat soil contamination, and reduce noise in our cities.”

“. . .A modest little idea we had to stage as a horticultural revolt. We were tired of what the mainstream gardening media had to offer—warmed-over garden tips, repurposed press releases about the ten thousandth new coleus on the market, dull little essays about the wonders of spring—and we were convinced that bloggers could overthrow the gardening establishment. Like all good revolutionaries, we began by writing a manifesto.” (Amy Stewart, cofounder of the Garden Rant blog platform).

I enjoyed the pieces about urban farming (Yolanda Burrell); the young farmers’ movement (Severine von Tscharner Fleming); the organic Seed Alliance (Cara Loriz); the Berry Botanic Garden in Portland Oregon, where Julie Kierstead Nelson started a seed bank for rare and endangered plants of the Pacific Northwest; the work of Martha Schwartz at Harvard showing compelling results from integrating afforestation into urban landscapes; Fern Verrow farm in Herefordshire, England, where Jane Scotter and her husband grow food for chef Skye Gyngell at her restaurant Spring, in London; the work of Vandana Shiva and others in India to prevent the neem tree from being patented; Lauren Springer’s thirty-year career, introducing 50-60 new plants to the dry Intermountain West, providing more regionally-adapted resilient, beautiful plants; the Buehler Enabling Garden within the Chicago Botanic garden, a display garden made for people with disabilities, including PTSD “we do a lot of work with veterans who cope with hypervigilance. Here they can monitor the entry and exit points and feel protected by the walls without a sense of mystery.” (Barbara Kreski),

Photo Workman Publishing, Timber Press

Cultivating Place podcaster and Heritage Harvest Festival 2020 presenter Jennifer Jewell learned to love the outdoors and gardening from her parents. The award-winning author shares reflections and a recommendation for the perfect family gardening project, Compost Your Worries, Share Your Joys, on the HHF blog. Journey with Jewell to find silver linings during this challenging time.

And for those wanting to read more about women farmers and activists, see this blog post from the Food Tank. It’s one of their Lists

20 Heroines Revolutionizing Food Activism to Improve the Planet

 

Growing Potatoes

Potato plant emerging in spring.
Photo Kathryn Simmons

This is the second part of a monthly series on potatoes. Last month I talked about Planting potatoes. Now they are in the ground, we turn our attention to growing healthy plants and doing all we can to maximize the yield.

Frosted potato plants May 10., after two nights at 30F and 29F. I hope this didn’t happen to you! If you know a frost is coming, try to get the potatoes hilled, which protects more of the stem and leaves under the soil. This increases the likelihood the plants will be able to grow back.
Photo Pam Dawling

Potato development stages and crop requirements

  1. First the plant produces roots, stems and leaves. This vegetative state lasts 30–70 days. Bigger plants have more yield potential, so the goal for this stage is to produce robust large plants. Vegetative (leafy) growth of potatoes is favored by warm, 80°F (27°C) moist weather, but tuber growth is favored by cooler soil conditions of 60°F–70°F (15.5°C–21°C). This combination can be achieved either by planting in spring, when the soil temperature lags behind increasing air temperatures and is still cool enough for tuber formation, or by adding organic mulches to keep the soil cool if planting in early summer.
  2. Tuber formation (a two-week process) and branching of the stems comes next. All the tubers (potatoes!) that will grow on that plant are formed in those two weeks. The number of tubers produced per plant depends on hours of daylight, temperature and available water in that short period of tuber initiation. Watering stimulates the production of more tubers. 5 gal/yd2 (22.8 l/m2) is a good amount to supply when tuber formation begins. Short day length is optimal, with a night temperature of 54°F (12°C). If temperatures at night are 68°F (20°C), initiation will be reduced; and at 84°F (29°C), will be inhibited. High nitrogen also inhibits initiation. During this stage, leaf growth continues. Flowering can happen too, but it’s not essential, so don’t worry if you get few or no flowers. Hilling adds soil to the stems, encouraging stem growth and providing sites for tubers to form.
  3. Third, the tubers grow larger, but don’t increase in number. When the leaves start to turn pale, the plant has finished its leaf-growing stage and will be putting energy into sizing up the tubers under the ground. Adequate water and nutrients are important during this critical stage which lasts until the plant reaches maturity for that variety, up to 90 days. Try to ensure at least one inch (2.5 cm) of water per week, up until two weeks before harvest. Avoid very uneven watering, or overwatering, as hollow heart could result. The size of the tubers depends on various growing conditions. Two or three weeks after flowers appear (if they do), the baby potatoes will be 1–1.6″ (2.5–4 cm) across. The best temperature is around 65°F (18°C), and I’ve read that potato size decreases by 4% for every Fahrenheit degree (7% per Celsius degree) above the optimal. Spacing is another factor — we got large potatoes one summer because we had poor emergence and therefore wide spacing! The heat of the summer didn’t stop them.
Three flat-tined potato forks to the left, four round-tined digging forks to the right. Flat tines do less damage, usually.
Pam Dawling

Potatoes dug during this tuber-sizing-up period will be “new” potatoes, and not have the thick skins necessary for storage. If you dig your potatoes during this stage (or “snitch” some, leaving the rest of the plant growing), you will be happy short-term, but your final total yield will be less than if you grew all the tubers to full size. If you planned for this, and grew plenty, you will be happy now, and happy later!

  1. Finally, the tops naturally yellow and die. The skins of the tubers thicken, which makes them suitable for storage. No more growth is possible. Sometimes there are reasons to terminate potato growth early – see Early Harvest below for more about this.

Hilling potatoes

Start hilling (pulling soil up over the plants in a ridge) when the plants are 6” (15 cm) tall. Hill again two or three weeks later and two more weeks after that, if the plant canopy has not already closed over, making access impossible. Hilling also provides an opportunity for dealing with weeds, so if possible do this task in sunny breezy weather which won’t let the weeds re-root.

Rows of potatoes after hilling.
Photo Wren VIle

On a small scale, use a rake or standard hoe to pull soil up from the side of the row opposite to where you are standing. If you are sharing the job, one person can work each side of the row at the same time. If you are alone, turn round and work back when you get to the end of the row. Don’t be tempted to twist your arms around and move the soil up the side nearest you. You will damage your body by this distortion of your spine and shoulders!

At the next scale up, use a rototiller with a hilling attachment, or perhaps a wheel hoe with a hiller, if your soil and stamina allows. We have used a semi-manual planting method, making single furrows with our BCS walk-behind tiller, planting by hand in the furrows, then using the tiller again to cover the seed pieces and hill. Nowadays we use a tractor-mounted furrower that can make two furrows in each pass, and disks turned inwards in pairs to ridge the soil.

Alternatives to hilling potatoes

If you can’t hill, you can increase the effective depth of planting by covering the rows with thick straw or hay mulch. This is easiest to do immediately after planting, before the plants emerge. We don’t mulch our spring-planted potatoes because we want the soil to warm up some from its winter temperatures.

Potato plant emerging through hay mulch in early July.
Photo Pam Dawling

When we plant in June, we cover the seed pieces, then hill, then unroll round bales of spoiled hay immediately, like wall-to-wall carpeting. We choose this method to help keep the soil cooler through the summer. In warm conditions, deeper planting, hilling and thick organic mulches all help keep the plants cooler, as does irrigation.

Weed control for potatoes

Potatoes are sometimes said to be a “cleaning” crop, as if they did the weeding themselves. Not so! Any cleaning that takes place is a result of cultivation. As with many plants, the initial growth stage is the most critical for weed control. Hilling in sunny weather can deal with lots of weeds in a timely way, especially if the machine work is followed up by the crew passing through the field hoeing. Organic mulches also reduce weeds. Potatoes later in life produce a closed canopy that discourages more weeds from growing until the tops start to die. Mary Peet reports that potato yields were decreased 19% by a single red root pigweed per meter of row left in place for the entire season.

Flame weeding can be used for potato plants while they are small, as well (as for carrots and beets before emergence as we see here).
Photo Brittany Lewis

In wet weather it can be impossible to hill when you’d like to, and this is where flaming can save the day. Flaming is not an alternative to hilling, but it can be a way to buy time and deal with rampant weeds if the soil is too wet to hill. Potatoes may be flamed at 6″–12″ (15–30 cm) tall. Beyond that, flaming is not recommended. See ATTRA for more on flame weeding. Flaming when the potatoes are less than 8” (20 cm) tall is also an effective control measure for Colorado potato beetles (More on pests next month). Choose a warm sunny day when the pests are at the top of the plants. Flaming can kill 90% of the adults and 30% of the egg masses, according to ATTRA.

Early harvest of potatoes

Sometimes there are reasons to terminate potato growth early. If you need storable potatoes, cut, flame or mow the tops of the plants, and wait two weeks for the skins to thicken up. To test for storability, dig up two potatoes and rub them together, or rub them firmly with your thumb. If the skins rub off, wait a couple of days before trying again. If the skins are strong, go ahead and harvest. You might do this if you have a fast crop turnaround after spring-planted potatoes, such as we used to do when following our spring potatoes with our fall cabbage and broccoli. Another time I’ve brought potatoes to a rapid end was in England, when we got Late Blight. We cut and removed the diseased tops (so no spores went down into the soil), and were able to salvage the potatoes two or so weeks later. Back then, the recommendation was to burn the green tops. This would probably not be recommended these days. It made for a smoky fire we kept going for several days. Terrible air pollution!

For the earliest possible crop in a dry climate (but not the highest yield), plant “old” seed (ones with lots of hairy sprouts) in early spring, hold off on watering until the tubers are marble size, then give a single good watering at 5 gal/yd2 (22.8 l/m2).

While it’s tempting to dig up potatoes early, the yields will be higher if you wait till the tops die.
Photo Kathryn Simmons

Next month I will write about potato pests and diseases.

Root Crops in May

A tidy bed of young carrots in May. Photo Kathryn Simmons

Root Crops to Plant in Central Virginia in May

Potatoes: It’s OK to plant any time in May: See my post on planting potatoes

Sweet potatoes: We generally plant sweet potatoes around May 10, 16″ (40 cm) apart, with 4-4.5′ (1.2-1.4 m) between ridges, allowing 5’ (1.5 m) space at the edges of patch. We install drip irrigation on the ridges when using plastic mulch. It is ideal if the soil temperature is 65°F (18°C) for four consecutive days before planting.  Plant 2-3” (5-7 cm) deep, with at least 2 nodes in ground, and at least 2 leaves above ground.  If the slips are long, plant them diagonally or horizontally, rather than going into a deep vertical hole, where the soil will still be cold. See my post on sweet potato planting

Carrots: We direct sow our sixth bed of carrots in mid-May. We sow our first carrots in mid-February, and then sow every 2-3 weeks after that. Our soils are cold in February, but the seed comes to no harm in the ground, and it’s a job we can get done early. May is our last month for sowing carrots that we know will be sweet. If we need to, we also sow once a month in June and July, but the hot weather impairs the flavor. Our big storage carrot sowing in early August will taste good, because the weather cools as they grow.

Here in central Virginia, zone 7, on a sandy clay loam, we grow Danvers 126, a sturdy open pollinated variety suited to high production of bulk carrots. In the past I have grown Chantenay Red Core (65 days), a blocky variety with a blunt tip, 5″ (13 cm) long and 2″ (5 cm) at the shoulder. It resists splitting, and can deal with clay.

Any decent soil will grow some carrots, but the best ones grow in deep, loose, and fertile sandy loams with good moisture-holding capacity. Old books warn against using manure before carrots as it will make them fork. This refers to uncomposted manure, not to compost. Compost will increase yields, and even reduce the culls with some varieties. (Research by Daniel Brainard at Michigan State University.) Compost not only increases the organic matter in the soil, but also suppresses some diseases and nematodes (which can cause forked carrots).

Thin carrots promptly to get good yields.
Photo Bridget Aleshire

Sow carrots whenever the soil is below 95°F (35°C), so long as you can keep the surface damp. Aim to sow 30 seeds/ft (1/cm), 0.25-0.5″ (0.6-1.2 cm) deep. Some people sow in single rows 8-10” (20-25cm) apart. Others sow in bands 2″ (5 cm) wide, at 8” (20cm) apart, with one length of drip-tape serving two bands in one 16-24″ (40-60 cm) bed. Carrots do well on raised beds, because the soil stays loose and the roots can easily grow deep. Hard rain in the first 3 or 4 days after planting can dry to a crust which could stymie the emergence. To prevent this, if you get heavy rain, irrigate for half an hour each day afterwards until the carrots emerge. Some people use shade cloth to help keep the soil surface moist. There are precision seeders which save you from thinning, but most growers I know use an EarthWay seeder, and then thin. Some people mix inert materials with the seed to help get a spaced stand. Sand at 1 quart (1 liter) to 0.5 teaspoon (2.5 ml) seed per 25’ (8 m) of row, is one recipe, although I worry that sand will destroy the plastic parts of the Earthway seeder before long.  Some people bake old carrot seed to dilute the good new seed.

Carrots do very poorly with competition, so try to start early carrots in a bed that had only light weeds the year before. Later sowings can make use of the Stale Seedbed Technique, where the bed is prepared ahead of time, and one or more flushes of weeds are germinated and flamed or hoed off. We flame weed our carrot beds before the carrots emerge. See the Special Topic below.

Carrots thinned to 1″
Photo Kathryn Simmons

Get to the initial thinning as soon as you can, spacing to about 1” (2.5 cm) apart, weeding at the same time. We usually have someone with good eyesight and hand-eye co-ordination hoe between the rows the day before the hand-weeding. If you are in an area with Carrot Rust Fly (Carrot Root Fly), you will want to remove all thinnings and broken foliage from the field, so you don’t lure the low-flying pest with the wonderful smell of the broken leaves. We do a second thinning, to 3” (8cm) at the stage when the baby carrots can be used for salads. If we get more weeds, we might do another round of weeding before harvesting the full size carrots. If carrots are spaced too widely, they will be more likely to split, and the overall yield will be reduced.

Flats of celeriac seedlings.
Photo Kathryn Simmons

Celeriac: An eye-catching winter storage root vegetable. Celeriac is sometimes called “turnip-rooted celery”. Its flavor is starchier and sweeter than celery, with hints of parsley, and a nutty taste. Celeriac is slow growing, but easy to care for once established.

If you have a long growing season, you could direct sow celeriac 6-7 months before the first fall frost date, for a late fall harvest. Perhaps put a board over the seed row to keep the soil damp and cool until the seedlings emerge. For most of us, we don’t have that much time. So if you didn’t already start some celeriac plants, May is too late for this year. Plan to order seed next winter.

Transplant celeriac when plants are 2.5-3″/6-7.5 cm tall, once the weather seems settled and warm, after your last frost date. If the weather is cold, just wait. Falling apple blossom is a phenology sign that conditions are suitable. We transplant celeriac around May 7 (our last frost is expected April 28). Use rowcover if a cold spell arrives after you have planted them out, or if you know cold weather is likely to return.

Celeriac gets 12”/30 cm spacing, with 4 rows to a 4’/120 cm bed –  that’s about 10”/25 cm between rows. We found closer spacing doesn’t work in our humid climate, as poor air-flow encourages rot. The Virginia climate is actually on the warm side for this crop, it prefers cooler areas, but we have good success if we pay attention at a few critical times. Celeriac requires long steady growth, so the task of the grower is to prevent checks to growth (such as weeds!). It can tolerate frost quite well, so there is no hurry to harvest in the fall. It can benefit from side-dressing with compost during the growing season, or giving seaweed as a foliar spray. A pH of 5.8-6.7 is ideal.

Root Parsley: A less well-known member of the umbelliferae family, also known as Parsley root, Hamburg parsley, Dutch parsley and turnip-rooted parsley. The flavor is a cross between carrot, celery and parsnip.  Like celeriac, it is slow to germinate and slow to grow. 70-90 days to maturity from direct sown seed.

Root Crops to Harvest in Central Virginia in May

Young beet plants
Photo Wren Vile

Beets: We like the long Cylindra/Formanova/Forono ones which are 6’’ (15 cm) long, very tender and are easily cut into regular slices, for pickles or cooking (55 days to maturity, OP). Among round ones we like Ace (50 days to maturity, F1 hybrid), and Detroit Dark Red (60 days, OP). Detroit Crimson Globe is said to maintain better flavor in hot weather than most others, which can develop off-flavors.

Young bunched beets can be stored for 10 days at 32°F (0°C) and 95% humidity. Mature beets can be stored for 6 months or more at 32°F (0°C) and 95% humidity. Trimmed beets keep well in perforated plastic bags under refrigeration.

Carrots: Our first carrots (sown in mid-February) will be ready to harvest in early May. Harvesting carrots barely needs describing. You need to loosen the soil to the depth of the carrots, pull them out, trim and wash. Some growers remove the tops first, but then it can be harder to remove the roots from the ground. Some people store them without washing, but then cleaning them is harder than if done before the soil dries on them. Carrots store very well in a refrigerator, in a perforated plastic bag. If you have lots to store, it is best to sort them, ensuring no scrawny ones or damaged ones get stored. Don’t store with apples or other fruit, or large amounts of cut flowers, or sprouting crops. The ethylene these crops give off can spoil the taste of carrots, removing the sweetness and leaving them tasting a bit soapy.

Harvested kohlrabi.
Photo McCune Porter

Kohlrabi: An unusual vegetable, sure to attract attention and be a discussion piece. It is tender with a flavor between a cabbage and a turnip. This tasty, crunchy root-like vegetable is easy to grow and doesn’t wilt as soon as you harvest it. It is actually the swollen stem, rather than a genuine root, but it behaves like a root vegetable. It can be eaten raw (sliced or grated) or cooked. The kind most commonly grown is a pale green or purple globe with long-stemmed leaves. When the leaves are cut off leaving stubs it resembles a sputnik. In addition, the leaves are also edible.

Conditions for growing kohlrabi are much the same as for other brassicas. It does best in cool weather. In our zone 7 climate, kohlrabi, like other brassicas, can be grown in spring or fall.

Harvest when the kohlrabi are 2-3” (5-7.5 cm) in diameter or even up to softball size. If left growing for too long the swollen stem becomes woody. Cut them from the ground with a sturdy knife. The base of the globe can be quite fibrous, so cut either the wiry root just below the soil surface, or cut higher, leaving a small disc of the globe behind, attached to the root. Snip or lop off the leaves, perhaps leaving a small top-knot if the kohlrabi will be sold immediately. We harvest in spring from around May 10 to June 30, and in the fall from October 20 to November 15.

Kohlrabi stores well in perforated plastic bags in a walk-in cooler, offering flexibility about when it is used, which is always an advantage.

Radishes: Early May brings an end to our spring radishes. Our last sowing is April 10. After then it is too hot for radishes where we are. In July or early August we sow winter storage radishes, including daikon.

Turnips ready for harvest.
Photo Wren Vile

Turnips:  A reliable root vegetable in the brassica family. They are among the fastest growing crops other than leafy greens. In zone 7, we sow a small crop of turnips outdoors under rowcover March 15, or earlier if spring is mild. Although they grow best in cool weather, turnips have no trouble germinating at high temperatures, as when grown for a winter storage crop.

Turnips are also available in gourmet varieties, to be eaten small, young and tender, 35-50 days after sowing, up to 2” (5 cm) in diameter. The delicious F1 hybrid Hakurei, 38 days, a smooth white flat-round shape, with crisp sweet flesh, and hairless leaves, is the most famous of the gourmet varieties. Although best harvested small, they do retain quality for a short storage period.

Young turnips can be pulled, banded, washed and sold with tops intact. Prompt cooling is important to keep the leaves from wilting. Small spring turnips can be pulled by hand, without digging – ours are ready May 20, and we clear the last of them in early June, refrigerating them till mid-July if we have enough.

For manual harvest, loosen the roots with a digging fork as needed, then pull. Trim tops and tails in the field (or move to the shade if it’s hot). All foliage should be removed for successful long term storage. Cut cleanly between the leaves and the root. Then wash, drain and store. Prompt washing before the soil dries on the roots will make them easier to clean.

Storage in perforated plastic bags under refrigeration works well for us. Turnips will keep for about 4 months at temperatures close to freezing and humidity of 90-95%. Higher humidity will make them rot.

Cut and damaged roots do not store well. If you haven’t enough humans to feed them to, but you have milking animals, you could chop them (to prevent choking) and feed them to your livestock. Even moderate quantities will not flavor the milk.

Other Root Crops Tasks in Central Virginia in May

See my post next week on growing and hilling potatoes, including alternatives to hilling for wet conditions. Flamers are intended to kill small weeds, not big ones, but we successfully used our wand-type flamer to kill weeds in the potato patch one spring when it was too wet to hill the potatoes.

Special Root Crop Topic for May in Central Virginia: Flame-weeding

When we sow carrots, we sow about 12″ (30 cm) of beet seeds at one end of the bed – these are “Indicator Beets”. When the beets germinate, we know the carrots will be up the next day and today is the time to flame weed the carrot beds. Flame-weeding is a great way to get rid of millions of fast-growing weeds and leave the field free for the slow-growing carrots. We still have to weed and thin once or twice as the carrots (and weeds) grow, but it is much easier to see the carrots, and they grow better if the first flush of weeds has been flamed off.

Soil thermometer in a beet bed.
Photo Bridget Aleshire

As well as beets, I use a soil thermometer and a chart of days to germination of carrots and beets at various soil temperatures. The table shows that beets are always a bit quicker than carrots in germinating. This information is in Sustainable Market Farming, Knott’s Vegetable Growers’ Handbook and Nancy Bubel’s New Seed Starter’s Handbook.

Days to Germinate 50°F (10°C) 59°F (15°C) 68°F (20°C) 77°F (25°C) 86°F (30°C) 95°F (35°C)
Carrots 17.3 10.1 6.9 6.2 6.0 8.6
Beets 16.7 9.7 6.2 5.0 4.5 4.6

Figure out which day you will probably need to flame. As soon as you see the red loops of the indicator   beet seedlings breaking the surface, flame the carrots. (But look for carrots too, just in case). In summer we flame carrots on day 4 after sowing, because we have found that carrots can emerge on day 5 in summer temperatures. One snag we hit once was that the carrots were mistakenly sowed an inch deep, instead of near the surface. Of course, this delays emergence, so by the time the carrots made it through that inch of soil, many new weeds had sprung up too.

Once you get over the hesitation about using a fiercely hot propane burner, flame weeding is quick and easy. And boy, it saves so much hand weeding! We use a Red Dragon backpack flame weeder (without the backpack frame).  We use the hand-held flamer attached to a propane cylinder that is in a wheelbarrow pushed by a second person behind the first. This person also acts as a safety monitor, looking out for unwanted things (like hay mulch burning). Some growers mount the propane on a backpack frame, and work solo, but we prefer to include a second person (and in this picture, a third!).

Flame weeding a carrot bed.
Photo Kati Falger

The operator walks along the aisle between beds, and wafts the wand diagonally back and forth across the bed. It takes about 10 minutes for a 100’ (30 m) bed. Flame weeding can reduce hand-weeding to one hour/100’ (30 m). Flame weeding plus stale beds 3 or 4 times can reduce hand weeding to 6 minutes/100’ (30 m).