Sweet potato harvests over the years

Crew harvesting sweet potatoes. Photo Wren Vile

 In my 10/30/20 post Growing High Yielding Sweet Potatoes, I wrote

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.

Today I looked to see the “plenty” I had written in previous years, and was surprised not to find much! Every mid-October from 2012 to 2016, I mentioned sweet potato harvest, but many times it has been in passing, and mostly yield statistics (bragging or groaning). 2012 has the most detail on doing the harvest – read it below.

In 2019 we got a very nice yield and carried on eating sweet potatoes into September. Previously people seemed to lose interest in sweet potatoes in late May, and we would distribute our surplus to other people. This year we just kept eating and enjoying them. I can report that they did get wrinkly and grow big sprouts, but were still very tasty down to the last one in late September.

We now use electric fencing to keep the deer out, and grow on biodegradable plastic mulch to keep the weeds down, and use drip irrigation to grow the sweet potatoes up. These developments in our method became necessary over the years.

Yesterday we ate sweet potato leaves as a seasonal green. You can eat these throughout the growing season, but we usually don’t, as we hesitate to take away anything that is helping the tubers grow. But at harvest time, the leaves are about to return to the soil, so we clipped the vine tips and cooked them up. OK, interesting, never going to be a favorite for me, but perfectly acceptable, and less distracting than going off to harvest somehting else to eat in the middle of the big sweet potato harvest!

Sweet potatoes ready to crate up.
Photo Nina Gentle

Sweet Potato Harvest October 2016

10/11/16: Yesterday we started harvesting our sweet potatoes. Yields look OK but not fantastic. We had a lot of problems with deer eating our sweet potatoes this year. We did have a temporary electric fence, but we often didn’t pay it good attention and it grounded out. Next year the rotation brings the sweet potatoes to a more traveled location. I can’t believe I’m already doing that “Gardener Survival Strategy” of thinking “Next Year Everything Will Be Perfect”!!

 10/18/16: Our average first frost date is October 14. Actually from our own records it has averaged 10/22 over the last 11 years. . . .  It’s good to be prepared.

This post includes tips on DIY weather-forecasting, and preparations for fall frosts

Sweet potatoes sorted into boxes.
Photo McCune Porter

 Sweet Potato Harvest 2015

 10/20/15: We got our sweet potatoes all dug and safely indoors before Saturday night’s 27F and Sunday night’s 26F. Whew! Another Garden Year Milestone passed. We got about 223 boxes this year. The boxes contain about 23lbs each, so that’s 5129 lbs, plenty to feed 100 hungry people for six or seven months. . . .  Our average harvest for this size patch (about 700 plants) is 4035lbs. This year we got a yield of a little over 7lbs of sweet potatoes per plant. Last year’s record crop was 11lbs per plant.

 10/13/15: We are on the point of harvesting our sweet potatoes. After all the rain we had recently, we were waiting for the soil to dry enough to walk on. . . . I was worried for a couple of days that the weather would stay cold and the sweet potatoes might rot in the cold wet soil. One year when I was fairly new to Virginia I caused us to leave the sweet potatoes in the ground till early November (hoping they would grow a bit more) and then it rained hard and we ended up with a load of sweet potatoes that either rotted directly or else went through a transition to a hard uncookable state. I learned the hard way to harvest sweet potatoes before soil drops to 55F. This week I studied the soil thermometer and the max and min thermometer and was reassured by the warm sunny days. The soil has been drying out nicely. Tomorrow we start digging. It usually takes us three afternoons. Everything looks auspicious. No rain or horribly cold weather, enough people. . .

Crates of sweet potatoes selected for growing next year’s slips.
Photo Nina Gentle

Sweet Potato Harvest 2014

10/14/14: Our sweet potato harvest is huge this year! We mostly managed to keep the deer out of the plot, by luck and a scarecrow and things that fluttered in the breeze. We’ve filled all our usual boxes and then scrambled twice to find more! . . . . I counted the equivalent of 273 normal-sized boxes in the basement this morning. At 23 pounds for our standard box, that’s about 6280 pounds. We might be up to 6500 pounds by the time we’re done. This will be our record! I think our local food pantry will be getting some sweet potatoes this winter and next spring!

I compared sweet potato yields for different years. We usually have about 600 plants in 800 row feet (16″ spacing). Yield is about 11 pounds/sweet potato plant this year. But as they say “your results may vary.”  Ours certainly have. Working back from 2012, we harvested 4070 lbs, 2208 lbs, 1860 lbs, “lots” (poor record-keeping!), 5590 lbs, 3820 lbs and 4050 lbs in 2007.

Hauling sweet potatoes uphill the hard way. Sometimes we use the truck!
Photo Nina Gentle

Sweet Potato Harvest 2013

10/13/13, Sweet potatoes, statistics and inspiration: After a week of drizzle, it finally eased up and we started harvesting our sweet potatoes. . . .  As usual, we set the dug roots in clusters, so we could see which plants yielded most and chose medium-sized roots from those to grow our slips next year. . . . This year, the Georgia Jet seem more productive than the Beauregard – I think that’s usual. We dug about a third of the crop the first day and got 86 boxes. The second day we had a lot of other harvesting (beans and broccoli being the most time-consuming), so we only dug another 36 boxes. . . .

Well  . . .  the yield dropped off a lot where the deer had been browsing (memo: fence out the deer in future!) We got a total of 177 boxes of various sizes, perhaps about 3939 pounds, almost two tons. . . .

Our yearly harvest of sweet potatoes has varied a lot, from 31 boxes (a sad year) to 243 in 2009. An average over ten years of 112 boxes, each weighing perhaps 23 pounds. . . .  We always hope to have enough to last till the beginning of May, when people start to lose interest in sweet potatoes, and start hoping for tomatoes.

Sweet potato harvest.
Photo Nina Gentle

How we do our Sweet Potato Harvest 2012

10/12/12: Usually sweet potatoes are harvested the week the first frost typically occurs. . . . Contrary to myth, there is no toxin that moves from frozen leaves down into the roots. On the other hand, cold injury can ruin the crop, and roots without leaf cover are exposed to cold air temperatures, and have lost their method of pulling water up out of the soil. Cold wet soil can quickly rot sweet potatoes (I know, it’s happened here).

To harvest, we first remove the vines from the area to be harvested that day. There is usually 3 afternoons’ digging for ours, and we want to leave live vines to protect the rest of the crop overnight. We use pruners to snip the vines where they emerge from the soil, leaving stumps to show where to dig. We roll the vines into the spaces between the rows.

Using digging forks, we carefully dig up the roots, which grow in the ground in a bunch-of-bananas shape. We want to select good potatoes for seed, and we grow several different kinds (Georgia Jet, Beauregard, and a couple of heritage varieties whose names we don’t know), so we make sure not to mix potatoes from different rows. As we dig, we set the potatoes out beside the spot where they’ve grown, one clump per plant, so it’s easy to identify the most productive plants.

It’s important not to bruise the roots, or to leave them exposed to temperatures higher than 90°F (32°C) for more than half an hour, or they will get sun-scald. Below 55°F (13°C), they’ll get chilling injury. We also avoid any abrasion of the skin, which is very fragile at this stage. We leave the sweet potatoes to dry on the ground for 1-2 hours, unless the weather is unsuitable. This year we had ideal weather, not too hot, not too cold, breezy enough to dry the skins, sunny.

We want to grow our own slips (baby plants) next year, so we save at least 1 root per 5 slips wanted.  (1 good slip every 16″.) So to plant 800 row feet, (600 slips), we save 100 each of our two main varieties and 20 each of the two heirlooms. That should be plenty. Some will shrivel or rot, so we allow a margin. We don’t save for seed any roots that look diseased. We choose plants with a high yield and no string (rat-tail) roots. From these plants, we choose small-medium sized potatoes with typical shape and color.

When grading and crating the roots in the field, we first choose the seed potatoes, and then sort storable from “Use First” roots. Large open broken surfaces will cure and can be stored, but any roots with soft wet damaged areas or deep holes (whether from voles, bugs or fork tines) will not store, and should be graded out, for composting or immediate use. We sort into 4″ deep wood flats or 5″ plastic crates for curing, and buckets for the “Use First” category.

Boxes of sweet potatoes curing.
Photo Nina Gentle

Immediately after harvest, we take the boxes of sweet potatoes into a warm damp basement below the dining hall, to cure. This allows the skin to thicken, cuts to heal over and some of the starches to convert to sugars. Uncured “green” sweet potatoes are not very sweet at all, and are better used in dishes where they combine with other foods. A baked uncured sweet potato is a sad disappointment.

We stack our boxes of roots on pallets, and put wooden spacer sticks between boxes in each stack, to ensure airflow. We get quite good temperatures, but keeping humidity up is difficult for us. We cover the flats with newspaper to hold in some moisture. The best result seems to come from splashing water on the concrete floor several times each day. We use box fans to improve the airflow, and the basement already has some natural ventilation.

Ideal conditions for curing are 85-90°F (29-32°C), and 80-95% humidity for 4-7 days, with some airflow and ventilation. Curing takes longer if conditions are less than perfect. The length of the curing period also varies with the dryness of the soil just prior to harvest. We usually reckon on 10-14 days. . . . .

So – how did we do this year? Middle of the road, I’d say. Decent yields, but not a bumper crop – we still had empty boxes left over. The deer were regularly eating our vines until quite recently. Last year we had a dog to chase the deer off, but he met with a road accident. His replacement was old, and she just wanted to be a pet, so we had deer again. We used drip irrigation and biodegradable plastic mulch this year, and did a good job of weeding, so I put the lower yields down to deer damage.

Sweet potatoes on a plate.
Photo Brittany Lewis

Root Crops in October

Radish Quick Pickles
Photo by Bridget Aleshire

Root Crops to Plant in Central Virginia in October

We have now passed our last chances to sow root crops outdoors. But the exciting season in the hoophouse has just begun. In early October, we sow radishes in our hoophouse. See Root Crops in September for more about our succession of hoophouse radish sowing dates. We like Easter Egg (a multi-colored mix of red, plum, pink, purple and white varieties, that matures over several weeks), Cherry Belle, the fast, uniform red globes, and White Icicle, like baby daikon about 3” (7 cm) long. These three varieties all stay crunchy and tender. We have a dread of fibrous radishes! Most years we make a sowing at the beginning of October and another at the end, and these will feed us from early November until early February. The late October sowing lasts for 8 weeks, so it’s good to make sure we plant enough. Radishes do a lot to brighten up meals in December and January!

White Egg Turnips.
Photo Southern Exposure Seed Exchange

In mid-October (10/10-10/25), we sow our first of three plantings of hoophouse turnips. We like the very fast-growing and tender Hakurei hybrid. It has short hairless tops which also make good eating. We sow this variety on the south side of the bed, leaving the other 3 rows for the taller varieties. We also like Early White Egg and Oasis, which are not quite as uniform as Hakurei, but are OPs and the seed is much cheaper. They produce more greens, which we value too. In the north row we often grow Red Round, a beautiful red-skinned turnip with tall attractive leaves. We also like Scarlet Ohno Revival, which has the advantage of hairless leaves. This is an Open Source Seed Initiative variety. The OSSI pledge: “You have the freedom to use these OSSI-Pledged seeds in any way you choose. In return, you pledge not to restrict others’ use of these seeds or their derivatives by patents or other means, and to include this pledge with any transfer of these seeds or their derivatives.”.

We thin the turnips as needed. If we sowed thickly, the first thinnings become baby greens for salad. Once the turnips are the size of marbles, we like to thin the plants to 3” (7 cm) apart and cook them whole, roots and greens together. The next thinning is to 6” (15 cm) and from that point on, we harvest the greens and roots separately. We get a ratio of one bucket of roots to two buckets of greens, which fits our needs perfectly. We like to mix the roots, as the one quarter of red roots adds a pop to the appearance.

Root Crops to Harvest in Central Virginia in October

Misato Rose Winter Radish.
Photo Southern Exposure Seed Exchange

We can continue harvesting beets (and beet greens), carrots, horseradish, kohlrabi, radishes, turnips (and turnip greens), and winter radishes outdoors. Once we have had a decisive frost we can harvest parsnips – the frost really improves the flavor. Our 9/6 sowing of hoophouse radishes will start to mature.

See Washing, sorting and storing root crops in Root Crops in September

We tackle our process of clearing root crops and storing them, starting with celeriac (if we grew it this year). We start with the least cold tolerant roots and work our way to the most cold tolerant. This list is root crops only. See my list of Winter-Kill Temperatures of Cold-Hardy Winter Vegetables 2020 for a more complete picture of “Harvesting in Time”

Clear and store (in this order):

  • Sweet potatoes 50°F (10°C)
  • “White” Peruvian potatoes 32°F (0°C) approximately
  • Celeriac 20°F (°C)
  • Turnips 20°F (°C)
  • Winter radish 20°F (°C)
  • Beets 15-20°F (°C)
  • Kohlrabi, 15°F (°C)
  • Carrots 12° F (°C)
  • Parsnips 0°F (°C)
Bucket lid with holes for sorting root vegetables for storage.
Photo Wren Vile
  • Wash, and store roots in perforated plastic bags in refrigerator or root cellar. We use a special measuring bucket lid to help new workers determine if roots are big enough to store.
  • Harvest sweet potatoes before soil temperatures go much below 55°F (13°C), or night air goes below 50°F (10°C). See the Special Topic below.
  • Harvest white potatoes when the skins have thickened. (When the skin is undamaged after rubbing two together. About 2 weeks after the  tops die). See Harvesting Potatoes and Root Crops in June. Two or three days before harvesting, we spend the day removing the hay mulch from our 1600 row feet (488 m) potato patch to the compost area. Our potato digging machine can’t deal with mulch or heavy weeds. To fit with using machinery, we clear complete rows. We have a Perfect Potato Harvest Checklist. For fall harvesting we do the tractor work in the morning and pick up the potatoes in the afternoon, avoiding leaving any out overnight if it will be frosty. (When harvesting the March-planted potatoes in July, we do the tractor work early in the morning and start picking up the potatoes as soon as possible. We aim not to be outdoors after lunch when it’s hot, but if we need to, we will, as we don’t want ready-baked potatoes sitting on the soil!) Tractor time is 4 hrs x 2 people. Picking time is 30 people-hours.
  • For beets, we allow 6 people-hours per bed (360 row feet (110 m), and expect 2-3 50-pound (23 k) bags per bed. Cut the stems about ¼” (6 mm) above the root, to reduce “bleeding” when you cook the beets. I was reminded recently that not everyone knows that the easiest way to cook beets is to scrub them, boil them in the skins, drain and immerse in cold water, then simply slide the skins off. Hardly any wasted food and no wasted time.
  • Bucket of freshly harvested Detroit Dark Red beets for storage.
    Photo Pam Dawling
  • For carrots, we allow 4.5-6.5 people-hours per (large) garden cart for washing, trimming and sorting. Plan to keep the last 15 minutes for clean-up. Divide the rest of the time available by 3. Use 1/3 of the time for digging, 2/3 of the time for washing and sorting. Add time to take to storage. Record yields. We take the carrot tops back and spread them across the beds. (fall harvest only ). In the spring and summer we take carrot tops to the compost pile, as the smell can attract carrot rust root flies. In late fall it is too late to sow cover crops to protect the soil, and the flies have gone to overwinter wherever they do that, so we spread the tops over the beds to provide some protection for the soil.)
Carrot rust fly damage (or possibly carrot weevil) Photo Jessie Doyle
Carrot pest larvae: carrot rust fly I think. Maybe carrot weevil.
Photo Jessie Doyle

Special Root Crop Topic for October in Central Virginia:

Harvest sweet potatoes

Here’s our method:

First roll up the drip tape. Harvest on 3 mild days – generally in the week that your first frost usually occurs (10/7-14). We expect our whole harvest of 800 row feet (244 m) to take 80 people hours. Allow 1/3 of the time for snipping, 1/3 for digging, 1/3 for crating and schlepping. Digging takes a bit less time than either of the other jobs. Even a few hours exposed to temperatures below 50°F (10°C) will cause chilling injury. (Frost on the leaves does not of itself damage the roots). Don’t leave clipped plants uncovered overnight. Don’t leave sweet potatoes outdoors. Clip the vines, dig carefully, set the tubers in plant-clusters to dry on the soil. Select seed tubers (healthy med-size tubers from high-yielding plants, no rat-tails).  We save a generous 100 Georgia Jet, 100 Beauregard, 20 each of Bill Shane’s White and Jubilee. (These last two are unofficial names for varieties we were given and are maintaining for genetic diversity.)

Sweet potato harvest.
Photo Nina Gentle

Other Root Crop Tasks in Central Virginia in October:

Curing sweet potatoes and white potatoes

Cure sweet potatoes in collapsible, stackable holey crates (or in wooden flats with spacers for ventilation) and cover with newspaper on top, in a basement with the heater on, for 10-14 days (85-90°F, 27-32°C, 80-90% humidity) or longer if it’s cooler and drier.  Use fans. Splash water on floor. Curing is complete when the skin is undamaged after rubbing two together. Restack the boxes (in a rodent-proof storage cage, if you are using an outbuilding).

Cure freshly harvested white potatoes in a root cellar at 60-75°F (15.5-24°C) for 2 weeks, with good ventilation, then cool cellar to lower temperature. See Special Topic for July. For weeks 2-4, the temperature goal is 50°F (10°C), and fresh air is needed about once a week. Our method of providing an air change in our cellar or adjusting the temperature is to leave the door open when the temperature will be closer to our goal than the current reality. It works well enough.

Planning to grow potatoes again

Planning to grow potatoes again 

Potato plant emerging in spring.
Photo Kathryn Simmons

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

I have a whole chapter about potatoes in Sustainable Market Farming, where the basics of potato growing can be found. Below are more details about growing potatoes that you may not have wanted or needed this year. Use your own records and this information to plan for bigger harvests, at times of year suited to your farm.

Varieties

Some varieties store better than others, so advance planning will help achieve good results. Scrutinize the small print in the seed catalogs before your next seed order.

Covering a row of seed potato pieces aligned under a rope.
Photo Ira Wallace
Photo Ira Wallace

Potato types: determinate and indeterminate

We have mostly grown Red Pontiac, Yukon Gold and Kennebec. They all seem to be determinate varieties — they grow as a bush, then flower and die. I only learned this year that there are determinate (varieties with naturally self-limiting growth, generally “early” varieties) and indeterminate varieties (such as “Russet Nugget,” “Nicola,” “German Butterball” and “Elba”). The distinction is explained in Potato Bag Gardening. Growers using towers, grow bags, and cage systems want indeterminate potatoes, which continue to produce more layers of tubers on the stems as they are progressively covered with more soil. Growers wanting a fast reliable crop in the field mostly choose determinate types, which grow as a bush, then flower and die. The Internet does seem to have some contradictory statements about which varieties are determinate and which indeterminate, and some dedicated container growers make assertions not supported by experienced commercial growers. So Reader Beware! I trust Extension and here’s a link to their Ask an Expert page on potato types.

Crop rotation, including cover crops

This is very important for potatoes, which are nightshades like potatoes, peppers and eggplant. Colorado potato beetles emerge from the soil in spring and walk (they don’t fly at this stage) towards the nearest nightshades they can detect. Give them a long hike! A distance of 750′ (230 m) or more from last year’s nightshade plots should keep them away. A three- or four-year rotation out of nightshades in each plot is ideal.

Suitable cover crops before potatoes include brassicas (which can help reduce root knot nematodes and Verticillium), Japanese millet (which can reduce Rhizoctonia) and cereals in general. Beware beets, buckwheat and legumes such as red and crimson clovers, and some peas and beans, as these can host Rhizoctonia and scab.

Late corn undersown with oats, mowed high in October to deal with weeds, and the ex-sweet potato patch sown in winter wheat and crimson clover. Credit Ezra Freeman

In our ten year crop rotation, our March-planted potatoes follow a winter of oats and soy (which winter-kill in our zone 7a climate). This cover crop is undersown in our late sweet corn about 30 days after sowing. Our June-planted potatoes follow a winter cover crop mix of winter wheat or winter rye and crimson clover. This mix is sown in early-mid October after our middle planting of sweet corn. (Yes, we risk the clover.) We had read that potatoes are said to do well after corn, so when we set up our crop rotation, that’s what we did. I have no scientific proof that the assertion is true, but we often have good potatoes, so at least it does no obvious harm!

Fall broccoli transplanted after July potato harvest, and undersown with a mixed clover cover crop.
Photo Nina Gentle.

After harvesting our March-planted potatoes in mid-July, we regularly did a fast-turnaround and transplanted our fall broccoli and cabbage in late July. We undersowed that with a clover mix 4 weeks after planting the brassicas. We kept the clover mix for an all-year Green Fallow, right round until the February a year and a half later. This fast-turnaround was a bit nerve-wracking, so we no longer do that, simply following the potatoes with the clover mix, while transplanting the brassicas in another plot.

After harvesting our June-planted potatoes in October, we sow winter wheat or winter rye with crimson clover or Austrian Winter Peas, depending when we are ready to sow. (Wheat and clover if by 10/15, rye and peas if later)

Preparing the Soil

A bed ready for tilling after mowing the cover crop and spreading compost.
Photo Pam Dawling

Potatoes benefit from generous amounts of compost or other organic matter (they use 10 tons/ac, 22,400 kg/ha) and will grow in soils with a pH of 5.0–6.5. They use high amounts of phosphorus (P) and potassium (K), and need adequate soil levels of iron and manganese. They are less affected by low levels of copper and boron. Hay mulch can be a good source of K. As Carol Deppe points out, potatoes will still produce an OK crop in poor soil, where you might not be able to grow much else. See the ATTRA publication Potatoes: Organic Production and Marketing.

Dormancy

See Part 5, Storing Potatoes, for an introduction to this topic. When potatoes sprout and whether they grow one or more sprouts, can be controlled by manipulating the storage conditions.

For extra-early spring planting, aim to sprout relatively few eyes per potato, so that relatively few shoots will grow and the seed pieces will be big enough, with enough nutrients for the plants. Do this by priming the seed potatoes at 65°F (18°C) until the eyes at the rose end just start to sprout. Store at 45°F (7°C) until two weeks before planting time, then finish the sprouting in warmth and light. The early sprouting of the rose-end eyes suppresses the sprouting of the other eyes. If needed, break off extra sprouts before planting.

To avoid sprouting, keep the potatoes below 50F (10C) once they are more than a month from harvest, avoid excess moisture, and avoid “physiological aging” of the potatoes, caused by stressing them with fluctuating temperatures, among other things. If eating potatoes do start to develop sprouts, it’s a good idea to rub off the sprouts as soon as possible, because the sprouting will produce ethylene, which will encourage more sprouting.

Physiological age of seed potatoes

Seed potatoes can act differently depending on their “physiological age.” The warmer the conditions are after dormancy ends, the quicker the sprouts grow and the faster the tubers “age.” When we buy seed potatoes the storage conditions they have already received are beyond our control. As a guide, the length of the longest sprout, and the number of sprouts are measures of physiological age (if the sprouting has taken place in the light). Varieties do not all show these effects to the same degree.

Don’t let your potatoes sprout in storage
Photo Jesse Strassburg

Deliberately adjusting storage temperatures is a way of manipulating the physiological age, in order to get higher yields or earlier maturity. To age seed potatoes, buy the seed in late fall or early winter before they break dormancy and store them rose (eye) end up in daylight at 50°F (10°C) until just before the planting date. In spring, reduce the temperature just before planting, to minimize the thermal shock from the cold soil.

Physiologically “young” tubers will have just one or two sprouts, due to apical dominance (when the leading bud inhibits the other eyes from developing shoots). The plants will have fewer stems, leading to fewer, but larger, potatoes. They will need longer to grow, and so give a later harvest. If you hurry and dig them early, you will only get low yields.

“Middle-aged” tubers give the best yields (27% higher than young or old tubers). “Middle-aged” seed potatoes have multiple short sprouts, without the hairy look of “old” ones. The pre-sprouting instructions given in Part One: Planting potatoes aim to produce “middle-aged” seed.

Physiologically “old” seed potatoes will have many “hairy-looking” branched sprouts, coming from eyes all over the potato. These potato plants emerge faster and start tuber formation sooner. The final plant size will be smaller (because the shoots are weak) and the plants will be more susceptible to drought and die sooner. Because the tubers do mature quickly, they may be good if you seek an early harvest, or are planting a fall crop a bit too close to the frost date. The total yield will be lower (but earlier) than from “younger” seed.

See the University of Maine Extension Service Bulletin #2412, Potato Facts: Selecting, Cutting and Handling Potato Seed  Their drawings are reproduced here. Also see Know and Grow Vegetables by Salter, Bleasdale, et al. for more on this complex topic.

More POTATO resources

The University of Maryland Extension Home and Garden Info Center Potatoes

University of Maryland IPM series on potatoes, which is a troubleshooter sheet on causes and solutions for problems

Cornell 2016 Organic Production and IPM Guide for Potatoes (104 pages)

The Potato Association of America, Commercial Potato Production in North America 2010. (90 pages)

The Government of Canada Biofungicides provide Post-harvest Disease Protection in Potatoes

Other related Blog Posts

Potato Research on Harvest and Storage

What Makes Potatoes Sprout, Nov 2017

How to Deal with Green Potatoes (one of my most-read blog posts!)

Green Potato Myths and 10 Steps to Safe Potato Eating in Mother Earth News

Root Crops in September

 

Root Crops in September

Cherry Belle radishes in the fall.
Photo Pam Dawling

Root Crops to Plant in Central Virginia in September

In September the days get shorter and we get our last chance to plant crops to feed us during the winter. Much more of our garden time will be spent harvesting this month!

In early September we can direct sow several root crops.

  • Daikon and other winter radish (in very early September);
  • Turnips (by 9/15);
  • Kohlrabi only takes 60 days from sowing to harvest. They can be direct sown or transplanted from flats or an outdoor nursery seedbed at the beginning of September. Kohlrabi is hardy to about 15°F (-9.4°C). Our night temperatures will be higher than that until the beginning of November;
  • Small radishes by mid-September. We usually squeeze these in on the south shoulder of a bed of kale, because they grow quickly and we don’t need a whole bedful. By the time the kale needs the space, the radishes will be gone.
  • In the hoophouse, we start our winter crops by sowing radishes and leafy greens on 9/6 or 9/7.
A bed of young growing turnips.
Photo Pam Dawling

See Root Crops in August for more details on these.

It’s too late for any slow-growing crops like carrots. We can just squeeze in some beets at the beginning of September, if we take good care of them. Hoeing, weeding and thinning at the first opportunity will help them grow a bit faster and make up for lost time. We could cover them with rowcover to warm their airspace and soil, once we have got them established and tidied up. I hate to cover weedy crops with rowcover – you just know it encourages weeds to grow faster! Beets won’t die of cold until 12F for my favorite, Cylindra, so they have quite a while yet. See Root Crops in August for more about fall beets.

Radish succession crops

In our winter hoophouse, we sow radishes six or seven times. It is a science and an art to time the sowings to provide a succession of delectable little radishes with no gaps in supply and no overlap of plantings and gnarly big roots. I have made a graph of radish sowing and harvesting dates to help us even out our supply.

Here’s a chart. 1/25 is our last worthwhile sowing date for hoophouse radishes.

Radish #1 sown 9/6 Harvest 10/5 – 11/15
            #2 sown 10/1 Harvest 11/6 – 12/25
            #3 sown 10/30 Harvest 12/16 – 2/7
            #4 sown 11/29 Harvest 1/16 – 2/25
            #5 sown 12/23 Harvest 2/19 – 3/16
White Icicle radishes in our hoophouse in winter. Photo Pam Dawling

Root Crops to Harvest in Central Virginia in September

During September, the root crops we can harvest include beets (and beet greens), carrots, radishes, turnips and horseradish (which I have more to say about below). We hold off on parsnips, if we have grown those, as the flavor improves a lot after a frost.

We could harvest potatoes, which I have written about in Potato Harvesting and Root Crops in June. We hold off on sweet potatoes until October, and I’ll write about them in a post of their own in a few weeks. If you need to harvest earlier, read the chapter in Sustainable Market Farming.

Special Root Crop Topic for September in Central Virginia: Horseradish

Horseradish plant.
Photo Harvest to Table

Horseradish, Armoracia rusticana, a perennial, is very easily propagated from pieces of root. It can be hard to get rid of if you change your mind! It’s wise to plant your perennial food crops in a special place that isn’t part of your annual crop rotation space. Remove all perennial weeds before planting horseradish or any other perennial vegetable. Ours is beside our grape vines, near our rhubarb. Full sun or partial shade will work. Horseradish looks like a big bad dock growing, but is in fact a brassica. Horseradish can provide value-added products for out-of-season sales, as well as a pungent treat in cold weather.

Horseradish root.
Photo GrowVeg

Buy or beg crowns or root pieces, and plant them 4-6 weeks before your average last frost date. Horseradish grows best in cool, damp regions with temperatures between 45°F (7°C) and 75°F (24°C). But in central Virginia, temperatures go from 0°F (-18°C) and 100°F (38°C) and we have more than enough horseradish, so don’t worry too much about that temperature range.

Plant crowns just at soil level. Plant root pieces with the top just below the surface and the bottom end covered with 2-3’ (5-8 cm) of soil. Space horseradish plants 24-36” (60-90 cm) apart. If you are worried about it spreading into important nearby plants, create a metal, wood or stone barrier 24” (60 cm) deep around the bed.

Keep the soil damp, add some compost once a year. You are unlikely to have any pest or disease problems with this crop. Young plants should not be harvested until the leaves are at least 12” (30 cm) long.

Horseradish plant.
Photo Nourse Farms

Horseradish is traditionally harvested September-April (the months with R in them!). The roots go as much as 2 ft (60 cm) deep and are very strong (but not as sturdy as gobo, Chinese burdock). Use a strong shovel, spade or digging fork, and start loosening the roots from 6” (15 cm) away. If you hear or feel a root snap, be glad! The goal is to extract some of the roots and firm up whatever remains, to continue growing. Water the plants after harvest if the weather is dry.

Collect the harvested root parts in a bucket, and wash them right away. You can store them dirty, but it is harder to get them clean later. Harvested roots can be refrigerated for several months until used – they seem fairly impervious to rot.

When you process horseradish do it outdoors, with googles on. I kid you not! This can be a good porch activity in sunny chilly weather. After thoroughly washing and scrubbing the roots, peel them carefully. Throw the peelings in the trash, not the compost pile, as they easily regrow from tiny pieces!

The peeled roots can be ground up in a food processor, to make relish or sauce. Or if you prefer, use a fine grater.

Harvested horseradish roots.
Photo Wikipedia Kren_Verkauf

If you want to buy plants, try Nourse Farms

If you’d like to read more about horseradish, including container plants grown as an annual, there’s info on Harvest to Table

If you’d like to read how to make the condiment, see Barbara Pleasant’s article on GrowVeg

Other Root Crop Tasks in Central Virginia in September: Washing, sorting and storing root crops

Harvesting

How you harvest roots depends on the scale of your farm and the equipment you have. For example, with carrots, you can mow or tear off the tops, then undercut with machinery, then lift. Or you can use the tops to help get the carrots out of ground, as we do, loosening them with a digging fork, then trim.

Ensure gentle treatment and no bruising of roots while harvesting. As we all know, it is important to avoid bacterial contamination. Wounds and abrasions can lead the crop to pick up new bacteria from the environment. Crops can be punctured by sharp edges of containers as well as the more obvious knives and fingernails.

The wash-pack house at Finca Marta, Artemisa, Cuba
Photo Pam Dawling

Trimming

Our method is to bring the harvested roots to a shady spot to trim, wash, sort and bag. We have a printed sheet, optimistically called “Perfect Vegetable Storage” to help us remember from year to year the tips we have learned. Usually we need scissors or knives for a clean cut, and usually we aim to leave about ¼” (0.5 cm) of leaf-stems attached to roots. It might be quicker to tear the leaves off, but this doesn’t give such good results and can cause the crop to need extra storage space. When we harvest carrots for immediate use, we snap the tops off right at the junction of the foliage and the root. When we harvest for storage, we trim with scissors to leave a small length of greens.

Washing and rinsing

After washing, and perhaps before, comes cooling. Make full use of all possibilities, such as damp burlap, or high percentage shade cloth, or the shade of trees, buildings, or a truck. At the washing station, crops may be sprayed down on a mesh table, or dunked in troughs or buckets of clean water. Washing can also act to cool the crop.

Draining away the water is important. Drain on a mesh table or in a holey bucket, a suspended mesh bag or laundry basket. Barrel root washers have the draining stage built in. We don’t have a rotary barrel root washer, much as we’d like one. Here’s our manual method.

  1. As you cut, gently drop the roots into buckets of water. This lets the dirt wash itself off to some extent, as you continue to cut more. Use whatever size and type of container seems most efficient.
  2. When the wash container is full, switch from trimming to washing: rub each root with your hands and drop it gently into a container of clean rinse water. Depending on the cleanliness of the roots after washing, it may be possible to reuse the rinse water. Or else make it be wash water for the next round. Once the water is quite dirty it needs to go. Gently pour it round a tree, or on the ground somewhere else. Avoid causing a washout by flinging a bucketful all in one place. Rinsing needs pretty clean water.
  3. When the rinse container is full, get two clean holey buckets. Take the roots one at a time out of the rinse water (don’t rub then any more, just lift them out). Sort as you go.
Harvested Purple Top Milan and White Egg turnips.
Photo Pam Dawling

Sorting storable roots from non-storable

  1. Decide if the root is Storable or is Use First (cull, or home use). Storable are sound, reasonably large. Use First may be small (less than ¾” diameter, less than 3” long, maybe) or damaged (deep holes, soft spots, fresh complex cracks). Open dry cracks or snapped-in-half roots may heal over and store just fine.
    Bucket lid with holes for sorting root vegetables for storage.
    Photo Wren Vile

    We made different sized holes in a special bucket lid, to help new people get an idea of size.

  2. Put the storable ones in one holey bucket and the non-storable (Use First) in the other. It helps to have 2 different colored buckets. It’s better to err on the side of calling doubtful ones Use First, but it’s even better to learn good sorting, as too many Use First roots can’t all be used quickly.
  3. When a Use First bucket is full, set it aside, or put on the cart or truck. Once a Storable bucket is full, set it aside to drain thoroughly before bagging. Do not confuse categories. Do more trimming, washing, rinsing, sorting.
  4. When the Storable roots have drained, get a well-perforated plastic sack. Ensure there are enough holes and big enough ones. Buy perforated bags or perforate your own. If you need more holes, the safest method is to lay the bag on the grass, stand on diagonally opposite corners, then stab the bag with a largish knife. Make about 3 cuts across the width of the bag and about 6? 7? 8? down the length. Or fold the bag and use a 3-ring paper hole punch in several places. Refold and repeat.
  5. Gently pour the Storable roots into the well-perforated bag. We usually use 50 pound bags. Tie the neck with a short length of rope and make a masking tape “flag” label with the date and the type of vegetable.
Sweet Potatoes in storage.
Photo Pam Dawling

Storing

When all the bags of storers have been gathered up, record the number going to the cooler on an Inventory clipboard. If there is no official tally sheet, make one on a full size sheet of paper.

We store bulk roots in a walk-in cooler, up on a high loft/shelf. Use pallets in the loft for better airflow under the bags. Start a new pallet for each different type of vegetable and for a substantially different date, eg fall carrots separate from spring carrots. Keep inventory: once a month, someone takes stock of what we have and updates the list.

See Root Crops in August for details on sorting newly stored potatoes

Storing potatoes

Potato crates in our root cellar.
Photo Nina Gentle

Storing potatoes

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 (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 my book, Sustainable Market Farming, and another on root cellars (including construction), where much of this information can be found.

This year’s new Victory Gardeners now need to learn how to store your harvest, so it can supply your household for as long a s possible. As more commercial growers aim to produce local food sustainably year-round, the storage of vegetables for sale over the winter becomes important. Understanding the needs of different crops can help reduce your electricity bill and carbon footprint, and maximize the amount of produce you can store for later sale. Only critical crops need refrigeration. Potatoes should not be refrigerated. Many others may be stored without electricity, perhaps in buildings that serve other uses at the height of the growing season.

Our in-ground root cellar. Photo McCune Porter

A 1978 publication from Washington State University Extension, Storing Vegetables and Fruits at Home, is a good introduction to alternatives to refrigerated storage, using pits, clamps and root cellars. There is also good information in USDA Agriculture Handbook 66. 2016 revision. Many growers are still using the 1986 version, but it’s worth checking newer recommendations and additional advice. UMass Extension has a good site on post-harvest and storage resources. Nancy and Mike Bubel’s book Root Cellaring has a wealth of information, including how to build a root cellar.

Don’t expect a one-shed-fits-all solution to crop storage. I identify five different sets of storage requirements, for different storage crops. This one is specific to potatoes, which don’t want colder conditions: Cool and moist: 40°F–50°F (5°C–10°C), 85%–90% humidity. With a good in-ground root cellar, potatoes can be stored for 5-8 months, but other options can also work. A max-min thermometer will help you keep the storage space in the right range.

We removed all the soil to renovate our root cellar roof. Photo McCune Porter

Reasonable expectations

Only store sound potatoes. Garbage in, garbage out. Damaged and poor quality vegetables will not store well. Always handle all crops for long-term storage gently, to avoid bruising. For long-term storage, make sure crops are fully mature but not over-mature when you harvest. Potatoes need firm skins that don’t rub off when you rub with a thumb. This is different from some crops, such as beets and sweet potatoes, that don’t have a “ripe” stage, but are ready when they reach the size you like. Very small vegetables don’t store well. Expect that a small percentage of your crops will go bad in storage — it’s not a sign of failure, just a reminder that life has limitations.

Cure, then store

Potatoes are one of those vegetables that need to cure before storage in conditions that are different from those needed for storage. Curing allows skins to harden and some of the starches to convert to sugars. See the post on Harvesting Potatoes in July. Potatoes need curing in moist air (90% humidity) for one to two weeks at 60°F–75°F (15°C–24°C). You may be surprised at how warm this is. Wounds in the skin will not heal below 50°F (10°C).

We sort our potatoes after two weeks of curing and find this usually reduces the chance of rot so that we don’t need to sort again. With potatoes, the rate of deterioration drops right down after a few weeks. Remember to keep white potatoes in the dark while curing as well as during storage.

When filling stackable crates, leave space for the crates to lock into each other.
Photo Nina Gentle

Preparation for storage

Plan your storage sites, buy a thermometer for each site, and gather suitable containers. Clean and prepare your storage space before going out to do a big harvest. Wood crates are good for nostalgia and agritourism, but plastic is kinder on aging backs and less likely to harbor diseases. Containers should rest on shelves, pallets or blocks of some kind, and not be set on bare concrete floors. This helps improve ventilation and reduce condensation.

For traditional storage without refrigeration, potatoes (and most other root crops) store best unwashed (less wrinkling), though this can make them harder to clean later. If you might not be able to keep temperatures low enough, choose stackable crates rather than closed bags. When you have choice in the matter, try to harvest potatoes from relatively dry soil, so they are less likely to grow mold. The packing of your containers should allow for airflow, but you don’t want the produce to shrivel up, so be observant. Sometimes night ventilation offers cooler, drier air than you can get in the daytime. Keeping root cellar temperatures within a narrow range takes human intervention, or sophisticated thermostats and vents. If needed, electric fans can be used to force air through a building.

Ethylene

Ethylene is an odorless, colorless gas, generally associated with ripening, sprouting and rotting. Chilling, wounding and pathogen attack can all induce ethylene formation in damaged crops.

Some crops, including most cut greens, are not very sensitive to ethylene and so can be stored in the same space as ethylene-producing crops. Potatoes are very sensitive to ethylene and will sprout in a high-ethylene environment.

Some crops, such as ripening fruits, produce ethylene gas while in storage. Don’t be tempted to set that bargain box of very ripe bananas you bought on the way home near anything you don’t want to sprout or ripen further. Propane heaters and combustion engines produce ethylene. Be careful if using your garage to store potatoes.

Our 10’ x 11.5’ (3 x 3.5 m) cellar will hold 10,800 pounds (4900 kg), or around 5 tons (tonnes)of potatoes. Photo Pam Dawling

Basement storage rooms and root cellars

Traditional root cellars are made by excavating a large hole near the house, lining it with block or stone-work walls, casting a well-supported and well-insulated concrete roof, then covering the top with a big mound of soil. The doorway may have bulkhead doors or an entry way with additional doors. The more modern version is to construct an insulated cellar in the basement of a building such as a CSA distribution barn or your house. See the Bubels’ book, or the Washington State publication for drawings and instructions on making these. Provide wide doorways with ground-level access if possible (roll that garden cart right in!). Good lighting and drainage are important, so you can see if everything is storing well, or hose the shelves and floor down if it isn’t. Mouse-proofing is worth considering upfront. Our 10’ x 11.5’ (3 x 3.5 m) cellar will hold 360 crates with an ample central path. That’s 10,800 pounds (4900 kg), or around 5 tons (tonnes).

Black snakes control mice in the root cellar. Photo by Nina Gentle

 Root Cellar Ecosystem

Store potatoes in a moist, completely dark cellar, ideally at 40°F (5°C), up to 50°F (10°C). Ventilate as needed during times of cool temperatures, to maintain the cellar in the ideal range. We need to actively manage conditions in our root cellar to cure the potatoes and help them store well. We have no automated ventilation, or even ventilation ducts. We simply leave the door open at night when we want to cool it down, or in the daytime in winter. We just choose a time when the forecast temperature is in the range we’re aiming for. Yes, mice do come in the open door! We encourage black snakes to live in our cellar, to keep the mice under control. (How do we encourage snakes? I mean we don’t drive them out, and if we need to, we move one or two in there.) This can be a bit unnerving, as the cellar is dark. (We chose not to have a light, as leaving it on by accident could cause a lot of potato greening before we noticed our mistake.) We have developed a special door-opening technique so we can co-exist with the snakes, who like to hang out on the top of the doorframe. We unlatch the door, open it a crack, then bang it closed, before opening it fully. Any resting snakes have by then dropped to the floor where we can see them and avoid them. (No snakes have been hurt in this process!) People who don’t like snakes will be really motivated to fit a rodent-proof vent system!

I wrote a blog post about Root cellar potato storage, on 8/07/2018. It includes a fuller version of our Root Cellar Warden instructions below. Here is the shorter, post-harvest version of our “Root Cellar Warden” instructions:

  • After the potato harvest, the potatoes need to be at 60-75F (15-24C) with good ventilation for two weeks. Leave the door open on mild nights (or days) every 2 or 3 days, and close it later. The newly harvested potato is still respiring and needs fresh air. Lack of sufficient oxygen during curing results in Black Heart, a condition where the tubers develop nasty black lumps of dead tissue in the centers, so be sure to provide good ventilation during curing.
  • After 14 days, the potatoes need sorting to remove Use First and Compost ones. Usually this is done by bringing the crates outdoors. You will need buckets, rags, gloves. It’s important to do this in the 3rd week after harvest, and not leave it longer, to minimize the spread of rot. Keep the crates away from walls, which sometimes collect condensation. The potatoes benefit from the airflow if they are not touching the walls.
  • After 14 days, cool the cellar whenever a mild night or chilly day is forecast, down to 40-45F (4.5-7C).
Sorting potatoes two weeks after harvest.
Photo Wren Vile

Dormancy Requirements of Potatoes

We researched the dormancy requirements of potatoes in an effort to store ours so they don’t sprout when we don’t want them to.

What I know so far about dormancy is that potatoes need a dormancy period of 4-8 weeks after harvest before they will sprout. So if you plan to dig up an early crop and immediately replant some of the potatoes for a later crop, take this into account. Get around this problem by refrigerating them for 16 days, then chitting them in the light for 2 weeks. The company of apples, bananas or onions will help them sprout by emitting ethylene.

To avoid sprouting, keep the potatoes below 50F (10C) once they are more than a month from harvest, avoid excess moisture, and avoid “physiological aging” of the potatoes, caused by stressing them with fluctuating temperatures, among other things. If eating potatoes do start to develop sprouts, it’s a good idea to rub off the sprouts as soon as possible, because the sprouting process affects the flavor, making them sweet in the same way that low temperatures do.

I have also written blog posts about

Potato Research on Harvest and Storage,

What Makes Potatoes Sprout,

How to Deal with Green Potatoes (one of my most-read blog posts!)

and if you still want to read more about potatoes,

Book Review “Potato: a history of the propitious esculent” John Reader, Yale University Press 2008

Read a whole book about the potato. Abe Books, John Reader

Organic and Alternative Methods for Potato Sprout Control in Storage

Mary Jo Frazier and colleagues at the University of Idaho Extension, in 2004, researched the use of essential oils of mint and cloves to inhibit sprouting in storage. These plant oils can add 20-30 days storage, and then need to be reapplied. There is the issue of flavors carrying over into the tubers.

Other biocontrols to reduce storage losses

There has been some USDA ARS (Agricultural Research Service) research into biological disease control for stored fruit and vegetables. It takes three directions:

  • Using biologicals such as Aspire yeast, Bio-Save Bacteria (Pseudomonas syringae) or chitins to form a semi-permeable film over the surface of the roots and fruits;
  • UV light to induce rot resistance. Primarily used for fruit;
  • Natural fungicides derived from jasmine and peaches, which induce disease resistance in the crop itself.

Currently these methods are only used by large operations, but in the future, they may be useful to small growers.

Potato harvest.
Photo Nina Gentle

Root Crops in August

Root Crops in August

Misato Rose Winter Radish.
Photo Southern Exposure Seed Exchange
China Rose Winter Radish.   Monticello Shop

Root Crops to Plant in Central Virginia in August

Like July, August is not a good month for sowing many root crops in Virginia – it’s very hot. However, the daylight is getting shorter and so the hot part of the day is also getting shorter.  And the calendar is boxing us in. The month of August is when we establish crops that will feed us in the fall and winter.

Carrots:

On August 4, we sow our fall carrots, enough to store and feed us all winter. Twin Oaks can eat 30+ bags (50 lbs, 23 kg each) of carrots during the winter, so we try hard to grow a big crop of fall carrots. See Root Crops in May for more about sowing and growing carrots, including pre-emergence flame weeding.

Good irrigation is important for successful carrot growing in hot weather.
Photo Bridget Aleshire

Carrots do very poorly with competition, so try to grow them in a bed that had only light weeds. You can use 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. Carrots do well on raised beds, because the soil stays loose and the roots can easily grow deep.

Some people bake old carrot seed to dilute the good new seed, to reduce the thinning work and the wasted seeds. 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.

Hard rain in the first 3 or 4 days after planting can dry to a crust that could prevent emergence. 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.

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. The idea is to flame the beds the day before the carrots are due to emerge.

Table of days to germination of beets and carrots at various temperatures

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

If we are unable to get our fall carrot sowing finished in early August, we sow them in late August. We try to avoid sowing in the middle of August when the hordes of baby grasshoppers emerge. If we have to sow in the middle of August, we use hoops and fine mesh ProtekNet, battened down well around the edges to keep the pests out. The hoops hold the netting up above the foliage, keeping it inaccessible to insects.

Beets

Beets can be tricky to germinate in hot weather, but to get a good storable-sized root, we need to get them established by 8/20 at the latest. (Our first frost date is 10/15 to give you an idea of when things cool down.) We get ready to sow on 8/1, but sometimes we wait for a cooler spell. I like the Cylindra beet. The shape is long (good for slicing), the skins come off easily, and the flavor is very sweet and the texture tender.

Young Cylindra beets.
Photo Wren Vile

We direct sow either dry beet seed, or some we have presoaked for 1-2 hours. Beet seed drowns easily: don’t use too much water or soak for too long.  Either way, sow 1/2″-1″ (1-2.5 cm) deep, tamp the soil firmly so that the seed is in good contact with the soil and its life-saving water supply. Keep the row damp, by watering daily as needed for the 4-6 days they take to emerge. Beets prefer 50°F–85°F (10°C–29°C). Some people lay boards over the seeded rows but then you have to be sure to check frequently and remove the boards when the seedlings emerge. Other options include covering the beds with shadecloth on hoops, or making some other temporary screen to the south side.

Turnips:

I mentioned turnips in July as a crop to harvest. That was the spring-sown turnips. We sow our fall turnips 8/15 or up until 9/15 (our absolute latest). Turnips can be up the next day, even at 95°F (35°C). Most will be Purple Top White Globe for winter storage. Because of the high populations of harlequin bugs, and sometimes aphids or flea beetles, and cabbage caterpillars, we hoop and net all our fall brassicas. We like ProtekNet (for smaller amounts than a whole roll, try Johnnys)

Brassica transplants under ProtekNet. (I couldn’t find a photo with turnips) Photo Bridget Aleshire

Winter radish:

In central Virginia, we sow winter radish on August 4. They have no trouble germinating at high temperatures. We like to grow Misato Rose, Miyashige Daikon and Shunkyo Semi-Long.

China Rose winter radish.
Photo Southern Exposure Seed Exchange

Kohlrabi:

Early Purple Vienna and Early White Vienna can still be sown here in August. They take only 60 days from sowing to harvest. They can be direct sown or transplanted from flats or an outdoor nursery seedbed. Kohlrabi is hardy to maybe 15°F (-9.4°C). It doesn’t get that cold here before the beginning of November, so counting back 31 days in October, plus 30 in September, plus 31 in August – that’s 92 days already, more than enough. We can sow kohlrabi in early August and get a crop at the end of October.

Purple kohlrabi
Photo Small Farm Central

For fall brassica crops, we use an outdoor nursery seedbed and bare root transplants, because this fits best with our facilities and our style. Having the seedlings directly in the soil “drought-proofs” them to some extent; they can form deep roots and don’t dry out so fast. Other people might prefer to sow in flats.

We cover the beds with ProtekNet insect mesh on wire hoops until the plants are big enough to stand up for themselves against “pest bullying”. Overly thick rowcover or rowcover resting directly on the plants can make the seedlings more likely to die of fungal diseases in hot weather – good airflow is vital.

We aim to transplant most brassicas at four true leaves (3-4 weeks after sowing). In hot weather, use younger transplants than you would in spring, because larger plants can wilt from high transpiration losses. If we find ourselves transplanting older plants, we remove a couple of the older leaves to reduce these losses.

Fall radishes:

Easter Egg radish seedlings in early September.
Photo Pam Dawling

We direct sow small radishes from mid-August (best) to mid-September (latest). Our favorite is Easter Egg, a mix with a range of colors that don’t all mature on the same day, but feed us over a couple of weeks. They are less likely to get fibrous than Cherry Belle or Sparkler types.

Root Crops to Harvest in Central Virginia in August

Carrots:

I usually reckon on three months from sowing to harvest for carrots, but they can be faster in warm weather. See Root Crops in June for more on carrots. If you sowed carrots in May, they should be ready to harvest in August. Don’t delay or they will become woody in texture and soapy in flavor. I suppose they are still nutritious, so if this has happened to you, blend into soups or make flavorful stews.

Turnip thinnings:

A few weeks after sowing, you will need to thin your turnips. You can use the tiny thinnings as microgreens for salad, and the bigger ones (with marble-sized turnips attached) can be gently steamed or braised.

Potatoes being harvested.
Credit Kathryn Simmons

Potatoes:

Depending when you planted your potatoes, they could be ready from mid-June onwards. They take about 4 months to reach maturity, so during August, potatoes planted in April will become ready.

See Potato Harvesting and Root Crops in June for more on harvesting. For best storability, wait until two weeks after tops have died to harvest. During that time, the skins will toughen up and you’ll have fewer harvest injuries. Potatoes can bruise! They may look tough and inert, but they are living plant matter and should not be thrown or banged about. To test if potatoes are ready to store, 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. see next weekk’s post for more on storing potatoes.

Other Root Crop Tasks in Central Virginia in August: sorting potatoes, thinning carrots and turnips

Sort potatoes

Sort potatoes two weeks after storing. Transfer the potatoes individually into clean crates, checking them for any dampness or softness. We triage (sort into three categories); those good to continue in storage, those fit only for the compost bin and anything we’re not sure about, but hope is not a total loss. We take these optimistically to our kitchen and plan to use them soon, if necessary cutting away bad portions. We find that this single sorting two weeks after putting the potatoes into storage can make all the difference. Most potatoes have “declared themselves” as fit or not by this point. Removing the rotting ones prevents the rot spreading. Often this is the only sorting we do. If you have time (or no bags of pasta in the pantry), you could aim to sort once a month until deep in the winter.

Sorting potatoes two weeks after harvest, to remove problems.
Photo Wren Vile

Ventilate the root cellar every few nights when it is coolest. Gradually get temperature down to 65°F (18°C). Try not to have temperature reversals. You don’t want to chill the potatoes yet – they are still breathing and need time to settle into dormancy.

Next week’s post will be devoted to storing potatoes successfully. It will be Part 5 of my Potatoes series. If you’re reading this in the southern hemisphere, you can use the Search box to find information of planting potatoes. Just add or subtract six months from my accounts.

Carrot thinning:

It is much easier to see the carrots, and they grow better if the first flush of weeds has been flamed off. Get to the initial thinning of carrots 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), 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.

Carrot row thinned to one inch.
Photo Kathryn Simmons

Mowing:

Keep edges mowed, and any buckwheat cover crop not seeding, so that you don’t encourage grasshoppers.

Special Root Crop Topic for August in Central Virginia: Sowing and transplanting when soils are hot.

There are definitely some challenges to getting seeds germinated in hot weather. And a different set of challenges to transplanting (not so applicable to root crops, as most are direct-seeded.)

 Here are some tips to try:

  • Choose suitable varieties. Read the catalog descriptions carefully. Look for flavor, productivity, disease resistance and cold-hardiness as well as heat-resistance. The crops you sow now need to emerge in hot weather and keep growing into cold weather.
  • Consider direct-seeding crops rather than transplanting them. They can be more cold-tolerant, probably because there’s no damage to the taproot. And transplants can struggle to recover from transplanting when it’s very hot.
  • Good soil preparation is important. Avoid over-cultivating before planting, as this makes crusting more likely.
  • Water a day ahead of sowing or transplanting, to reduce the need to water copiously afterwards. Pre-water furrows for large-seeded crops (I can’t think of any root crops with large seeds, off the top of my head).
  • Plant seeds deeper than you would in spring, as the soil is already warm and you want to guard against the seeds drying out. In cold weather we are guarding against seed rotting in cold wet soil.
  • You could sprinkle sand, grass clippings, straw or sawdust lightly along the rows.
  • After sowing, watering should be shallow and frequent, using fresh-drawn cold water, not something from a hose in the sunshine. For close-planted small seeded crops, use overhead sprinklers. Chilled water, night watering, and even ice on top of the rows can help reduce soil temperatures as well as supplying vital moisture.
If using a nursery seed bed, you can put ice cubes on top of rows of seeds in hot weather to help cool the soil.
Photo Bell Oaks

Sowing when soils are hot

Check the germination requirements for your crop (see Sustainable Market Farming), and the expected number of days to emergence under your field conditions, and use a soil thermometer.

If the soil temperature is too high for good germination, cool a small part of the outdoors. You could use the shade from other plants, shadecloth, boards, or damp burlap bags. For crops you normally direct seed, consider cooling a small nursery bed for your seedlings and transplanting later.

If outdoors is too challengingly hot, start your seeds indoors. Put a sown flat in a plastic bag in your refrigerator or in a cool room. Try the basement floor, perhaps. Cover flats with wet newspapers until the seedlings emerge. You could use plug flats or soil blocks rather than open flats, to reduce transplant shock.

Soaking seeds – a help when temperatures are high and soils are dry.

The length of time to soak a seed depends on its size: bigger seeds can benefit from a longer soak. Soak large seeds like beans and peas overnight before planting. It helps them get all the water they need to absorb for the initial sprouting. After that the smaller amounts needed to emerge are more easily found. Don’t soak legumes so long that the seed coat splits, or they lose nutrients and may get attacked by fungi.

Smaller seeds may only need to soak for 1-2 hours. I suspect that when I’ve had failures with soaked beet seeds, I soaked them for too long and they suffocated from a shortage of oxygen. Small seeds that have been soaked tend to clump together, so after draining off as much water as possible, mix them with a dry material like uncooked corn grits, oatmeal or bran, or use coffee grounds or sand to make them easier to sow thinly.

If you are using a seeder, spread your soaked or sprouted seeds out in a tray for a while to dry the surfaces. Experiment on a small scale ahead of a big planting, to make sure your seeder doesn’t just grind the seeds up, or snap off any little sprouts.

Pre-sprouting seeds to plant

To pre-sprout seeds, first soak them in a jar, then drain off the remaining water and put them in a cool place. Rinse twice a day, draining off the water. Sprout the seed just until you see it has germinated. For most crops 0.2″ (5 mm) is enough. Seeds with long sprouts are hard to plant without snapping off the shoot. If your pre-sprouting has got ahead of the weather or the soil conditions, slow down growth by putting the seed in the refrigerator. If you have leftover soaked or pre-sprouted seeds, you can store them in the fridge while the others come up, and then use them to fill gaps.

Harvesting potatoes

Harvesting potatoes and sorting storable from others.
Photo Nina Gentle

Harvesting potatoes

This is the fourth 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 (June)

PART FOUR: Harvesting potatoes (This one, 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! Harvest for immediate use anytime you’d like after the tubers reach a big enough size.

Picking up lifted potatoes and crating them.
Photo Nina Gentle

Preparing for potato harvest

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. Avoid irrigating at the end of the growing period or the potatoes may develop hollow heart, make knobby secondary growths or even crack. For maximum yield, and to harvest for storage, wait until the tops are completely dead.

In England, we planted in spring and harvested in October, waiting for the frost to kill the vines. In Virginia, we plant in March and June, harvesting in July and October. For our unmulched March-planted July harvest, we mow two weeks before our planned harvest, to fit a tight crop turnaround. In hot weather the cut tops and weeds dry up. If more weeds grow, we mow again the day before harvest. For our fall-harvested crop, planted and mulched in June, we need to remove the mulch after the mowing and before the harvest. This is a slow job, but necessary, and the mulch makes a good addition to our compost pile. If it looks like rains will delay the harvest, or nights are forecast to be very frosty, we delay de-mulching until the day before harvest.

Varieties such as Red Pontiac, Yukon Gold and Kennebec are determinate — they grow as a bush, then flower and die. If you have indeterminate varieties such as Russet Nugget, Nicola, German Butterball or Elba, you will need to kill the vines. I’ll come back to the topic of determinate and indeterminate varieties in Part Six, Planning to grow potatoes again (September). You can bring about an early vine death by mowing or flaming. This will also remove weed growth that could interfere with your digging equipment.

Potato harvest in progress. Note the line up of garden carts to haul away the bounty. Photo Nina Gentle

Whether the vines die naturally at the end of their lifespan, or they die of disease, or the frost kills them, or you do it yourself by mowing or flaming, it helps storability to wait 2-3 weeks more before harvesting to allow the skins to toughen up. They become more resistant to scrapes and bruises) and the potatoes become higher in dry matter. Harvesting is also easier if the vines are well dead. Test by digging up a sample and rubbing the skins. When the skins don’t break, the potatoes are storable.

Be sure to have enough crates, buckets, totes, gloves and workers. Clean and air the root cellar and warm it to 70°F (21°C).

Harvesting your potatoes

If possible, harvest when the soil moisture is 60-80% of field capacity. Not too dry, not too wet. This reduces damage from scraping. Ideally the soil temperature will be 45°-65°F (7°-18°C).  Because soil temperature lags 3-4 hours behind air temperature rise each day, in cold weather, try to harvest late in the day, but with time to finish before dark. In hot weather, harvest in the morning as early as possible. Tuber temperature will also affect bruise and rot susceptibility. Do not harvest when tuber temperatures are below 45°F (7°C) or above 85°F (30°C).

To use our potato digger we have to remove the mulch first.
Photo Twin Oaks Community

We use a Checchi and Magli single-row side delivery SP100 harvester. It does a good job in clean soil and an excellent job in clean fairly dry soil but gets stuck if we have a lot of organic material on the soil (weeds or mulch). The 1-row Potato Digger from US Small Farm Equipment, which a neighboring farm bought, has the same challenge. If using a digger, don’t set it too deep, or too much soil will be dumped on the harvested potatoes.

During harvest, someone walks alongside the tractor with a long-handled hook/claw tool, to clear blockages and hook any potatoes from the path of the tractor wheels. The rest of the crew follows, picking up and sorting the potatoes. If they are wet, we leave them to dry for a short time. We sort the damaged ones into “Farm Use” buckets and crate up the good ones. We try not to leave any potato parts in the field, to reduce the chance of spreading diseases.

When freshly harvested, potatoes are tender, breathing things. Avoid bruising, which is damage that does not break the skin, by not dropping potatoes more than 6” (15 cm), or throwing them towards a container. Don’t bang them to knock off extra soil. In hot weather we aim to work until done and not leave any potatoes in the field baking for long. In cold weather we aim to get done before nightfall and not have any freeze overnight!

Chain of people moving crates of potatoes from the truck to stack under a big pine tree.
Photo Nina Gentle

When harvesting in summer, we stack the crates of potatoes covered with a tarp, under a big tree overnight to lose some of the field heat before moving them to the root cellar early next morning. For the fall harvest, if the weather is chilly, we take the crates straight into the root cellar. Potatoes you take from storage can be no better than the quality of the potatoes you put into storage!

Potato harvesting raises rocks to the surface, so we try to find time soon after the potato harvest to collect them for use in road repairs and construction.

Yields are likely to be 150 lbs/100ft (223 kg/100m); 200 lbs/100 ft (300 kg/100m) or more is a good yield; double this is possible. In my book Sustainable Market Farming, in the potato chapter, I made a mistake and gave these as pounds per acre, which would be a miserable yield! 5 gallon buckets and square plastic “milk” crates hold about 30 lbs each (14 kg)

Post-harvest two week curing

After harvest, potatoes need to cure for two weeks at a surprisingly warm temperature: 60°F–75°F (15.5°C–24°C), and 95% humidity. While curing, the root cellar will need 6-9 hours of ventilation every two or three days. The potatoes are still actively respiring, so they need a good oxygen supply. Failure to ventilate enough can lead to Blackheart, where the inner tissue of the potatoes dies and turns black.

Potatoes will heat up if left closed in. Ventilate when the temperature is 0-20 F° (0-11 C°) cooler than your goal: air in the daytime if nights are too cold and days are mild; at night if nights are mild and days too warm. Try hard to avoid having the cellar cool down, then warm up. That causes the potatoes to sprout. If there is too much condensation, use a fan and open the cellar doors, when temperatures are closest to the goal. During the curing period, the skins toughen up more, and cut surfaces and superficial wounds heal over, enabling long-term storage.

Sorting potatoes in early November.
Photo Wren Vile

Sorting and preparing for long-term storage

After two weeks, we sort through the whole storage crop for rot, We find that this single thorough sorting can remove almost all of the storage problems that are going to happen. Not sorting at this point lets rots spread.

After the curing period, the potatoes become more dormant and do not respire so actively. Fresh air is needed about once a week in weeks 2-4, after which air exchange is not needed. Relative humidity should be 90-95%, to keep weight loss to a minimum, but not 100%! If the cellar is too warm, you will need to ventilate to lower the temperature.

Once potatoes are more than a month from harvest, the temperature, should be 40°-50°F (4.4°-10°C), and closer to the lower end of the range is best for long-term storage. In summer we work hard to reduce the temperature to 50°F (10°C) for long-term storage, but in the winter we can reach 40°F (4.5°C). Constant temperatures or a steady decline is the goal, not dramatic fluctuations, as these can cause stress and physiological aging, which leads to sprouting. Hotter temperatures promote more rot, and age the potatoes faster, also leading to early sprouting.

Potatoes have a natural dormancy of 60-130 days (depending on the storage temperature). After that period, they will start to sprout.

I will address long-term storage and preventing sprouting in Part 5 next month.

Resources

The Potato Association of America, Commercial Potato Production in North America 2010.

2016 Organic Production and IPM Guide for Potatoes from Cornell has a big focus on dealing with diseases and pests.

Don’t let your potatoes sprout in storage (more next month)
Photo Jesse Strassburg

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

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.