2024 Spring Spinach Trials and previous ones

Our sparse spring 2024 late spring spinach variety trial.
Photo Pam Dawling

I have conducted trials of spinach varieties before, such as when our long-time favorite Tyee was dropped by the market. Now we need to look again.

Winter 2017-2018 spinach trials

February 5 photo of our 2017-2018 winter hoophouse spinach variety trial.
Photo Pam Dawling

We compared Avon, Reflect, Acadia, Escalade, and Renegade in the 2017-2018 winter in our hoophouse and outdoors. We were looking for a dark-leaved savoy type, with good cold tolerance and good bolt-resistance once spring arrives.

Our observations for the hoophouse were

  • Renegade made fast early growth in November and December
  • Acadia and Escalade won on early harvests (December and January).
  • The smoother-leaved Renegade had thinner leaves 4/10, and therefore a lower weight yield.
  • Acadia and Escalade won in the hoophouse on 4/24, for bolt resistance and thick leaves
  • Acadia won on bolt-resistance in the hoophouse on 5/1. Escalade was not far behind.
  • Reflect won on 4/25 over Avon on bolt-resistance in the 4th hoophouse planting.
  • Acadia won on 4/25 on bolt-resistance in the 5th hoophouse planting (late January).
  • There was no clear winner between Reflect and Avon on bolt-resistance in the late hoophouse transplanting from the 4th and 5th sowings.

For outdoor spring plantings:

  • Avon won on productivity over Renegade on 4/26
  • Reflect won over Acadia, Escalade on 3/21 and 4/26.
  • No winner between Avon and Renegade on 5/2
  • Reflect won over Avon on 5/2.
  • Reflect and Acadia won over Escalade for productivity on 5/2. Of the two, Acadia had better color.
  • Escalade may have been more bolt-resistant.

I also wrote about Success with Spinach for Fall, Winter and Spring. That post includes tips for growing spinach, as well as observations on varieties going into the winter.

From that complicated picture we could have chosen different varieties for different times and places, but we came down in favor of Acadia every time, with Escalade as a close second. Now I hear Acadia is being withdrawn and we must switch again.

Earlier winter spinach trials

Tyee spinach in our hoophouse in October 2002. Photo Twin Oaks Community

For those wanting to dig deeper, here are my earlier blogposts about spinach variety trials

Oct 4, 2016: Three spinach varieties (Tyee, Avon, Chevelle)

October 2016:  Sowing Tyee, Avon, Chevelle

Feb 21, 2017 : Spinach overwintered in a coldframe; Transplanting the last Tyee, alongside Reflect and Avon in spring.

February 6, 2018Spinach Variety Trials (Tyee, Chevelle, Avon, Reflect, Renegade, Escalade and Acadia) and Planting Plan. Details of the varieties.

April 10, 2018: Spinach Trials Update

2024 Spring Spinach Bolt-Resistance Trials

Meanwhile I agreed to trial five spinach varieties for bolt-resistance. It would be gratifying to have a spinach variety more resistant than Acadia. I sowed Sunangel, Tarsier, Seaside, Kolibri and Lizard to compare their bolt-resistance. Sowing from mid-March to early April is much later than I would normally do here in central Virginia, so it would be a real test. I had 4 sowing dates each a week apart and three reps of each variety to even out any “unfairness” due to differences between bed edges and middles. It was all over by June 7.

I kept a spreadsheet, and included air temperature high, rainfall, irrigation, and after a while, soil temperature every Friday when I did my monitoring.

I didn’t get to harvest any spinach from this trial, as the number of plants was small, but I did see some clear differences in bolt-resistance. Sunangel is clearly the least bolt-resistant, by a long way. Kolibri is clearly the most resistant of the five under our conditions. Tarsier was second to Kolibri after a gap.

Bolting Sunangel spinach on April 21.
Photo Pam Dawling

We had challenging conditions:

During March we had a lot of rain, and we were unable to till in the wheat cover crop and prepare the bed and sow when we hoped.

I pre-sprouted the seed for the first sowing (“3/15″) for a week, and sowed it 3/22, the same day as the second sowing. By then we had tilled the too-wet bed roughly.

A week later, 3/29, some cover crop was poking through and regrowing, and the soil was still very wet.

A week after that (4/5) the soil temp was 58F. Germination was poor for all varieties in the first three sowings. We made the fourth (last) sowing. The weather turned to drought (the bed got overhead irrigation once a week). Air temperatures reached 89F, although the soil was still 60F.

All germination rates were poor, some very poor, which I attribute to the conditions. The first sowing of Sunangel started bolting 4/21.

By 4/26 the soil temp had reached 70F

After three weeks of no rain, we got a lot, 1.8″ one week, 2.1” the next. Daytime temps reached the high 80’s.

On 5/31 we got an outbreak of what I think was downy mildew. All varieties were equally affected. The second sowing of Sunangel started bolting.

It was another week before the first sowings of the other varieties started bolting. Kolibri was noticeably most resistant in all sowing dates.

Our winter favorite, Acadia, is currently still available from High Mowing, Pinetree and Harris. Escalade and Kolibri are available from Stokes. Kolibri is good at bolt-resistance, but not DM resistance and I’ve no idea how it does in the winter. We can try it next winter. Space is the variety often grown commercially. It has high DM resistance and claims to be for all seasons.

What triggers bolting?

Hoophouse spinach Top row: bolting Renegade; nearer row: Escalade.
Photo Pam Dawling

I wrote a post a few years ago What makes vegetable crops bolt and how can I stop it?

This article from Michigan State University also does a good job of explaining how cold temperatures trigger bolting (flowering) in spinach and other crops.

Harvesting Alliums (onions, garlic and relatives)

Onions curing and drying in strings.
Credit Southern Exposure Seed Exchange

The allium family includes all kinds of onions, garlic, leeks, perennial onions such as potato onions, and also less well known alliums, mostly perennials.

This is the time of year for harvesting most alliums except leeks. (It’s the time for planting out leeks for fall and winter harvests.)

I have a whole series of Alliums for the month posts. Here’s a link to Alliums for June. It includes the starter for the list I provide here, of the relative timing of harvests for various alliums.

Order of Allium Harvests

Our allium harvests generally occur on these dates. Your dates will differ but you can expect this order of harvests:

  1. Nov 18–May 10: Onion scallions in the hoophouse
  2. Mar 15–May 31: Garlic scallions
  3. May 7–May 28: Garlic scapes
  4. May 10–Jun 30: Onion scallions outdoors
  5. May 25–Jun 10: Green bulb onions (Allium cepa)
  6. May 30–Jun 8: Hardneck garlic
  7. May 30–Jun 11: Potato onions ( cepa aggregatum) planted in fall
  8. Jun 6–Jun 25: Potato onions planted in January and February
  9. Jun 10: Shallot bulbs (cepa aggregatum), fall-planted. They are not fully hardy in zone 7a. I recommend storing bulbs and replanting in early spring instead
  10. Jun 11–Jun 12: Softneck garlic bulbs
  11. Jun 11–Jul 11: Bulb onions sown in fall, with slow spring-sown ones to Jul 26
  12. Jun 19–Jul 2: Cipollini (cepa cepa) Small bulb onions grown in a hoophouse from spring transplants
  13. Jun 30–Jul 5: Elephant garlic ( ampeloprasum ampeloprasum) We stopped growing this when too many winter-killed
  14. Jul 1–Jul 8: Shallots from bulbs refrigerated over the winter and replanted in early spring
  15. Jul 1–Jul 15: Cipollini outdoors from spring transplants
  16. July: L’itoi (A. cepa aggregatum). This peppery little perennial clumping onion sends up edible shoots in early July.
  17. Jul 4–Jul 30: Shallots from seed started in late January, plugs transplanted in March. Harvest 4–8 weeks later than those from bulbs replanted in October
  18. July–September: The small red-purple bulbils of Egyptian onions can be pickled. Earlier in the year, before the bulbils appear, harvest the tasty, succulent leaves of this very hardy perennial.
  19. Spring, summer, fall according to size: Welsh onions ( A. fistulosum) are non-bulbing, hardy perennial onion greens, larger than chives and scallions. Japanese bunching onions are similar. Can be sown in fall or spring. Clumps can be divided and replanted
  20. Sep 6: Shallots direct sown outdoors in February and March

Here’s some details on harvesting some of the smaller alliums

Harvesting onion scallions

Scallions ready-to-harvest.
Photo Pam Dawling

From around May 10, through June, our outdoor onion scallions are big enough to harvest (just as the hoophouse ones finish up!) We start these from seed in January and February and transplant as clumps in March and April. In cooler climates, you can schedule harvests through summer, but we cannot get good quality ones here after late June. It’s good to develop an efficient harvest method with little scallions or it takes way too long. To harvest, loosen the soil with a digging fork, then lift out a clump. Deal with scallions in bunches as much as possible, rather than one at a time. Shake the plants, and trim off the roots and the ragged tips. Holding the bunch in one hand, pass the scallions one at a time to the other hand, separating them and pulling off a single outer leaf, not more. Don’t fuss with them too much. Next set the scallions in water in a small bucket, to clean themselves while you work on the rest. If you are going to band them, start out with a bunch of rubber bands around three fingers on the hand that holds the bunches (leaving the forefinger free for tasks demanding dexterity). When you’re ready to band them, use the other hand to pull a rubber band into position. When the bucket is full enough, dunk the scallions up and down, and transfer them to a clean bucket with a small amount of water to keep them fresh.

Harvesting garlic scallions

A healthy patch of garlic scallions in spring
Photo credit Kathryn Simmons

Garlic scallions (small whole garlic plants) provide our first allium harvest of the calendar year, starting in mid-late March and continuing (if we have planted enough) into May. Some people cut the greens at 10″ (25 cm) tall and bunch them, allowing cuts to be made every two or three weeks. We prefer to simply lift the whole plant once it reaches about 7″–8″ (18–20 cm) tall. You may need to loosen the plants rather than just pulling. The leaves keep in better condition if still attached to the clove. Trim the roots, rinse, bundle, set in a small bucket with a little water, and you’re done! Garlic scallions can be sold in bunches of three to six depending on size.

Harvesting garlic scapes

Harvesting garlic scapes
Photo by Wren Vile

Another spring allium harvest is garlic scapes (the firm, edible flower stems of hardneck garlic).  Here scapes appear when tulip poplars flower. In a warm spring, that can be the end of April. Garlic scape arrival is partly temperature dependent. We harvest scapes two or three times a week for about three weeks, until there are no more. At the Roxbury Agriculture Institute at Philia Farm in New York State, they wait until the scape has curled round, then cut it off. We harvest ours sooner than that, in order to let the bulb grow as big as possible. We pull our garlic scapes to get the most out ! In our climate, the appearance of scapes indicates the garlic will be ready to harvest in three weeks. I’m not sure if the same timing works everywhere, so keep records and you’ll learn what to expect. Exactly how day-length and temperature interact as triggers for scape and bulb harvest dates, I don’t know. I’ve done some research, but haven’t found much solid info yet.  In general, plant flowering is triggered by some combination of enough vernalization (chilling hours — maybe 10 weeks below 40°F/4.5°C), plant maturity, temperature and photo-period (the relative length of day and night). In cold weather the plants suppress the flowering signal. The leaves perceive the amount of daylight, and when the temperature is also right, they trigger flowering by sending a signal (called Florigen) to the shoot tips. Florigen may be an actual compound, or may be some combination or ratio of several hormones produced by the plant. Almost all these factors are outside our control once the plant is in the ground, so the best we can do is pay attention and be ready to act.

Harvest garlic bulbs and bulbing onions

(see Alliums for June) I won’t go into details here, as I’ve done that previously.

240 heads of garlic drying in Tenax fencing.
Photo Sierran Farmer

Harvest small potato onions

produced by large ones planted in September.

Yellow Potato Onions.
Photo Southern Exposure Seed Exchange

Harvesting cipollini

(aka cocktail onions, boiling onions, pickling onions)

Red Marble cipollini.
Photo Fedco Seeds

These small, attractive onion bulbs can be easier to grow in marginal onion climates than full-sized onions or can be an additional allium crop. The larger ones can be used as fresh bunching onions. All may be cured. Cipollini naturally have more sugar than most onions, which makes them ideal for caramelizing or roasting whole. The scheduling and final size of your cipollini will depend on your latitude and temperatures.

Weed of the month: Docks in June

Dock weeds flowering and seeding in early June.
Photo Pam Dawling

 This is the second of my once-a-month series of posts focusing on weeds. One weed that is making itself very evident on our farm in late May and early June is the dock. We have both the broadleaf dock, Rumex obtusifolius L. and the narrow-leaved or curly dock, Rumex crispus L. Docks are in the buckwheat family.

Docks are tap-rooted perennial weeds, requiring different approaches to last month’s weed, the fast-seeding annual galinsoga.

Cover of Manage Weeds on Your Farm
SARE

See the excellent information on docks in the book, Manage Weeds on Your Farm: A Guide to Ecological Strategies, By Charles Mohler, Antonio DiTommaso and John Teasdale. Click the link to read my review. It’s a book worth having on your shelf and it’s also available online from SARE  It explains how to tackle various types of weeds in an ecological way and then profiles many individual weeds. With good clear photos of weeds at various stages of their lifecycle. Here you can find out what dock seedlings look like, and go and hoe them out before they get too big.

Another resource on ecological weed management is the ATTRA publication Sustainable Weed Management for Small and Medium-Scale Farms

When dock seeds germinate they first develop a rosette of leaves close to the ground. The rosette grows quite large (leaves can be 12″ by 6″ with broad-leafed docks, 12″ x 2.5″ for narrow-leafed docks), at which point most of us cannot simply pull the dock out as the tap root will be sturdy and long. You will need a digging fork or a shovel to get the root out. As with other tap-rooted perennial weeds, if the root breaks, the part remaining in the soil can regrow. The short, vertical underground stem that attaches to the roots regrows readily. In spring, new plants can also grow from fragments of the true root.

Broad-leafed docks have branching taproots, while the narrow-leafed docks have a single root, with almost no branches. If left to their own devices, the leaves become speckled with red  and the plant puts up a tall stem with clusters of inconspicuous reddish flowers. The flowers mature into winged fruits surrounding three-sided glossy reddish seeds.

Dock as a rosette. Photo University of Maryland Extension

Docks can become established in uncultivated but fertile areas, especially along edges of pastures or areas with long-term cover crops. frequent mowing before docks get a chance to grow large can help other plants to out-compete the docks. The key is to provide enough nitrogen for your crops but not more, or the docks will suck it all up! Vigorous crops can out-compete docks for light (part of why docks do well on edges where they have no competition).

If docks get too big and have flowering heads or even seed heads, it is best to dig them out and take them away. This is a good time of year for that, before the seeds mature and scatter. If I dig just one or two docks, I put them on the driveway to dry out and get road-killed by vehicles rolling over them. If we take advantage of a day with lots of help, especially after rain when the soil is easier to dig, we take wheelbarrows and make a team sport of it, digging all the docks from one area. We have a special place under trees that we call the End of the World, where we pile noxious weeds. The shade discourages them from regrowing, as does the sheer weight of the weeds we pile up.

On a larger scale, if a whole field has become infested with dock, say a pasture that you want to convert to growing annual crops, then stronger measures are called for. Disk or plow the field in midsummer (now!), and repeat the cultivations whenever the weather is suitable for drying out fresh root pieces that will get brought to the surface. I would not normally advocate repeated tillage and leaving soil bare, but annual crops are no match for established perennial weeds.

Narrowleaf or curly dock with a stem of still-green flowers. Photo University of Kentucky Dept of Plant and Soil Sciences

If you are using a rototiller, be sure to work down to a depth of four inches. If you till shallowly, you might just severe the neck from the root, allowing the dock to regrow. Run your machinery slowly and get maximum chewing-up action. When you see new shoots with 2” leaves growing, repeat the tilling. This is the stage at which the regenerated plant has extracted lots of nutrients from the root piece and has not yet paid much back. Don’t wait longer!

Winter cover crops can do a lot to suppress new dock seedlings as well as regrowths. The growth rate of docks is slow-and-steady, the opposite of galinsoga! Tackle docks before they disperse their seeds. Once shed, dock seeds are initially dormant for some months. Germination occurs at 50°F–95°F (10°C–35°C) with 68°F–77°F (20°C–25°C) optimal for fastest germination. Cooler nights and warmer days help speed germination, as does light exposure, unless filtered through overhead trees, which decreases germination. Flushes of seedlings tend to germinate in spring and fall.

Seeds of broadleaf dock can remain viable for 40 years, and those of narrowleaf dock can live in the soil as long as 80 years! But the rate of seed mortality each year is quite high. Manage Weeds on Your Farm quotes one experiment in Ontario, when less than 15% of curly dock seeds and 1% of broadleaf dock seeds survived more than one year.

Large dock weeds in early June
Photo Pam Dawling

Docks that survive the winter as rosettes make new growth in spring (February to March) and flower in April and May. Seeds mature a mere 6-18 days after flowers open. If you see flowering docks, don’t delay!

Both dock species are relatively short-lived perennials, nearly all dying within 4 years. By that time, they may have produced over 240,000 seeds.

Dock leaves are edible by people and pigs, but not cattle, horses or poultry. They may be cooked like spinach and many people find them very tasty.

Success with Growing Watermelons

Crimson Sweet Watermelon. Credit Southern Exposure Seed Exchange

 Watermelons are delicious as a snack on a hot day in the garden, helping improve your heat tolerance.  If lightly salted to balance the electrolytes, they can cure dehydration. The seeds, if well chewed to break up the indigestible seed coat, can provide amino acids, fatty acids, vitamin E, potassium and phosphorus. Watermelons are easily digested and add fiber to the diet. Second only to tomatoes as a source of lycopene (said to prevent some cancers), watermelons are also an excellent source of vitamin C, beta carotene, folic acid, biotin, potassium, magnesium and citrulline (an amino acid important for healing wounds and removing toxins from the body).

Watermelon Varieties

Amish Moon and Stars watermelon. Credit SESE

Watermelons are all Citrullus lanatus. After trying several varieties, we chose Crimson Sweet (85d from transplant, OP), a 20–25lb (9–11 kg), striped, 10″ x 12″ (25 x 30 cm) oval melon. It has tolerance to some strains of Anthracnose and Fusarium, and according to Southern Exposure Seed Exchange, it promotes beneficial soil fungi that inhibit Fusarium. We saved seed for many years, selecting for size, earliness, disease resistance and flavor. See Fruit of the Month for September for more about choosing varieties. At this point, you have probably made your choice for this year, and may have them in the ground.

Watermelon Crop Requirements and Yield

Watermelons do best in free-draining light soils that warm quickly in spring. Ensure high organic matter content, sufficient boron and a pH of 6.5. Black plastic mulch, either the removable or the biodegradable kind, will speed growth and ripening. If you want to use organic mulches, put them around the plants after the soil has warmed up, or you will delay the harvest. Drip irrigation is better than overhead, as it reduces the chance of foliar diseases. Water well during fruit development, then cut back during the harvest period for best flavor and to prevent fruit bursting. We often run our irrigation at the same time as harvesting, so we can easily check for leaks.

If drainage is an issue, make ridges or raised beds before planting. You can use straw or spoiled hay in the aisles to absorb some of the water. Watermelons easily die in waterlogged soil.

There are on average 24 seeds/g, 670/oz, 11,000/lb, 24,200/kg. Crimson Sweet seeds are about half the size of others, so need only half as much seed.

Yield of Crimson Sweet and other varieties can be 460lbs/1,000 ft2 (227 kg/m2). For our 6,600 ft2 patch, (613 m2) we can expect an average of 3,000lbs (1,400 kg), whether 150 melons at 20lbs (9 kg) or 300 at 10lbs (4.5 kg). We have got as many as 300 melons from this area, using 2′ x 5.5′ (0.6 x 1.7 m) spacing. More on spacing follows.

Dried watermelon seeds in a paper bag.
Photo Pam Dawling

Sowing Watermelon Seeds

Watermelon seeds need a soil temperature of at least 68°F (20°C) to germinate, taking 12 days at that temperature, but coming up in a mere 3 days at 95°F (35°C). If direct seeding, station-sow 4–6 seeds 1″–1.5″ (2.5–4 cm) deep at the final spacing. Later, thin the emerging seedlings to one or two at each spot. Pests are more likely to attack plants stressed by planting in cold conditions. If in doubt, wait.

Transplanting is the way to go for early melons. It allows young plants to be raised in close to ideal conditions, and it gives the soil time to warm up. We use Winstrip 50-cell ventilated plug flats for this crop, or soil blocks. Cells should be at least 1.5″ x 1.5″ (4 x 4 cm). We put two seeds in each cell and after emergence we pinch off the weaker seedling. We sow 30% more cells than we hope to take to the field, which is another 30% more than we need to plant because of their fragility. Casualties with melons are usually fatal. (We expect casualties on planting day.) We sow April 26.

They come up very fast in our hot germination chamber. Once the seedlings emerge, they need maximum light and warmth, but not too much watering. We transplant at 15–19 days old. Four weeks old is about the maximum for watermelons — they start to get stunted if held too long.

Watermelon transplants in a Winstrip tray on May 2nd. Photo Pam Dawling

Transplanting Watermelons

Don’t rush watermelon transplants into cold soils, it’s better to wait — cold conditions can permanently stunt them. Once outdoor daily mean temperatures have reached at least 60°F (15.5°C) and the first true leaf has fully opened, you can plant them out.

We have found watermelons to be amongst the crops needing the most skill at transplanting. The stems are fragile, the roots respond poorly to disturbance, and spending extra time later replacing the dead plants is frustrating and doesn’t lead to early melons. It also requires the grower to produce lots of spare plants, which all take time and care.

Pulling a roll of biodegradable mulch.
Credit Wren Vile

We roll out drip tape, test it for leaks and then unroll biodegradable plastic over the drip tape and shovel soil along all the edges of the mulch. See our method of using biodegradable plastic, setting it out by hand. The next day we turn on the irrigation while planting. This helps ensure no one stabs the drip tape, and the plants can be set by the emitters. (Yes, you can still find them, even though they are under the plastic.) Watermelon transplants can easily get leggy in the greenhouse, so make holes deep enough to bury the whole stem as well as the roots. We use pointed trowels to punch through the plastic.

We drape netting or rowcover over hoops. This prevents the cover abrading the leaves, creates a volume of warm air around the plants and keeps insect pests away. A week after transplanting, we fill any gaps with more transplants or with a few seeds station-sown at each spot where we want a plant. Sowing pre-sprouted seeds will help make up for lost time if something has gone wrong.

Watermelon Spacing

Spacing can make a difference to size and yield, but not sweetness. There are widely varying recommendations, from 9 ft2 (0.8 m2) to 80 ft2 (7.4 m2) each! The area is the important factor, so choose a row spacing that works nicely for you and adapt your in-row spacing to give the area you want for each plant.

 


Watermelons growing on (torn) plastic mulch. A tented row with rowcover is in the background. Photo Nina Gentle

We used to transplant our watermelons 2′ (60 cm) apart in rows 10′ (3 m) apart. I read about watermelons only needing 10 ft2 (0.9 m2) per plant, so we switched to a spacing of 2′ x 5.5′ (0.6 x 1.7 m), 11 ft2 (1 m2), in order to fit more plants in the space and therefore get more first and second melons. The new spacing seemed fine and the total yield was in the right range. We have tried 2.5′ (80 cm) in-row spacing, some at 3′ (90 cm) and some at 3.5′ (1.1 m). These spacings correspond to areas of almost 14 ft2 (1.3 m2), 16.5 ft2 (1.5 m2) and 19 ft2 (1.8 m2) each. We didn’t keep records and didn’t notice a difference in size. A Brazilian study on Crimson Sweet found that 13 ft2 (1.2 m2) per plant gave the highest total yield, but 15–20 ft2 (1.4–1.9 m2) gave bigger melons.

Factors in Deciding Watermelon Spacing

Total yield (by weight): reduced spacing (to a certain point) increases total yield. Reducing plant spacing 50% may increase the total yield by 37%–48%, while reducing the size of each melon only 10%-13%. Reduced spacing does not decrease the percentage of marketable fruit.

Yield/plant (by weight): decreases at close spacing, sometimes because the number of melons per plant is reduced, sometimes because the size of the fruit decreases. It is not a linear decrease.

Size: reduced plant spacing sometimes affects melon size, but not in a linear way. Other (environmental) factors affect melon size. Bigger varieties are more likely to have their size affected by closer spacing than small varieties are. Small size is an advantage in some markets.

Number of melons/plant: decreases as plant spacing is reduced, but not linearly. At close spacings, the difference is negligible.

Number of melons/area (fruit density): increases with plant density. More plants = more melons.

Early yield: variety, early transplanting, good conditions and hot weather will provide more early melons. The first melon on each plant is the early harvest. More plants means more first melons. Plastic mulch produces crops a month before organic mulch. Spacing has no influence on the ripening rate.

Sweetness: the flavor of watermelon is not related to the size of the ripe melon or the plant spacing. Healthy foliage and long hot sunny days are the biggest factors in building good flavor. August has shorter days than July, and September’s days are even shorter, so don’t expect late-season melons to be as sweet.

Plant health: overcrowding can increase foliar diseases, reducing photosynthesis and sweetness.

Labor requirement: closer spacing = more transplanting. More melons = more time harvesting.

Watermelon with healthy foliage and a flower. Photo Nina Gentle

Clarify your goals and choose your variety and spacing accordingly. If your goal is the highest weight of watermelons for a given area, plant Sugar Baby at 10–11 ft2 (0.9–1 m2) each. If your goal is the highest number of melons, try them even closer! But if you like Crimson Sweet and want fairly large melons, try 15 ft2 (1.4 m2) if 12lb (5.4 kg) melons are an acceptable size (you might still get 15lb/6.8 kg melons!). Otherwise, use 20 ft2 (1.9 m2). Go up to 30 ft2 (2.8 m2) if you want big melons and can accept a lower total yield.

Ideally, the ground will be filled with foliage by the time the first blossoms appear so that the crops can intercept and use all the available sunlight. Given that the market is for early melons, and early ones are sweeter, having many plants (one early melon each), and having them optimally cared for, is important.

Caring for the Watermelon Crop

Remove rowcover from transplants after three weeks (wait longer with direct sown crops) and remove netting once you see female flowers. Pollination is now the critical step, not warming. Pull any big weeds. (Cultivate between the rows if you have bare ground.) Water regularly — drip irrigation set out at planting is the best way to go, as there will be less chance of fungal diseases than with overhead watering.

Watermelons have separate male and female flowers on the same plant, and insect pollinators are necessary. Many species of native bees pollinate watermelons, but augmenting them with honeybees will help pollination, which means bigger, better-shaped melons as well as more of them.

Weeding is important and needs to be completed before the vines run. If big weeds get away from you and pulling them endangers the crop roots, wade in with pruners and clip off the weeds at ground level. This prevents the weeds seeding, and lets the melons get more sunlight again. Do not turn over the vines when weeding — cucurbits don’t like that! Removing damaged fruit will help the good ones grow better.

See Fruit of the Month for September for information on pests and diseases, harvesting and choosing varieties for next year. this material comes from my book, Sustainable Market Farming, where even more info can be found!

Ripe watermelons are a treasure! Photo Nina Gentle

Cicadas – the real story for Virginia

Top: Annual cicada. Credit Bugwood.
Bottom: Periodical Cicada. Credit Eric Day

Cicadas

Despite hype, cicada double-brood emergence won’t affect Virginia, Virginia Tech expert says

https://news.vt.edu/articles/2024/03/ext-cicada-double-brood-emergence-wont-affect-virginia.html

There are annual (“dog-day”) cicadas that emerge every year. Annual cicadas have black-green coloring, while periodical cicadas have black-red-orange coloring.

Annual cicadas, although noisy and large, are not at all dangerous to people. In fact, they are edible, but I do recommend removing the wings and legs first, otherwise it’s too much like eating crunchy food wrappers. Well, I suppose it is eating crunchy food wrappers! The flavor is mild, and the texture creamy.

Annual cicadas can damage young trees, because the females make slits in the bark of pencil-thickness twigs to lay their eggs. The overall effect is like pruning back the twigs about a foot. Not a problem on a big tree, but to be avoided on young trees if possible.

How do you protect young trees from cicadas? Cicadas emerge from the ground in a pupal shell, which they climb out of when they’re ready, splitting the top of the skin. You may have seen these cast shells still gripping on to siding or boards or other things that could be mistaken for a tree. Before too many emerge, cover your vulnerable new saplings with netting, or fabric. If you are a gardener, you may have rowcover or insect netting that will be perfect. If not, you may have old bedsheets or nylon net curtains. Keep the plants covered until no more cicadas are emerging. Cicadas die after laying eggs (I wonder when the males die?)

If you get the chance, stop and watch as an adult cicada emerges from its nymph shell. At first the wings will be crumpled and bright pink. Gradually they will stretch out and dry. Here’s a great little time lapse video of the process. In real life, it takes a bit longer! Note that it is the adult emerging from the nymph, not the nymph emerging.

The hype this year has been about the periodical cicadas. In particular, doomsayers have been trying to panic us into thinking we are all going to be battling a combination of the 13-year cicada and the 17-year cicada in some places. Mostly it’s not true.

Doug Pfeiffer, professor and Extension specialist in the Department of Entomology of Virginia Tech. explains “They have evolved this strategy of emerging all at once in order to overwhelm predators, a defense strategy called predator satiation.

“Periodical cicadas emerge after either 13 or 17 years, both prime numbers,” said Pfeiffer. “That is an adaptation to avoid predators who might develop a converging lifecycle and emerge to eat them.”

Each type of cicada exists as several Broods. Blacksburg, home of Virginia Tech, is on the very edge of the range of Brood XIX (19), a population of 13-year periodical cicadas produced from eggs laid in 2011, resting underground since then. Virginians living south of Caroline County and east of the Interstate 95 are probably seeing and hearing Brood XIX by now. Virginians living along the North Carolina border, especially those in Brunswick County, should also be on the lookout. See the map from Virginia Tech.

Virginia map showing likelihood of finding periodical cicadas in each county. Credit Virginia Tech Extension Service

People in the red zone will get no periodical cicadas. People in the bright green zones will probably get them. Other Virginians are in the maybe zones.

And the scary double-brood? A brood of 17-year cicadas (Brood XII) will also emerge in2024 – in Illinois! Very little geographical overlap!

When it is all over, the dead cicadas lie on the soil, feeding it as they decompose. The eggs hatch into tiny wingless nymphs, which walk down the tree and bury themselves in the ground, sheltering until it’s time to go above ground again, eating nutrients from plant roots.

Here’s a chart of when you can expect periodical cicadas in your neck of the Virginia woods:

Chart of cicada broods in Virginia

We are home to the 17 year brood II, last heard here in 2013. due back in 2030.

And here’s a map

East Coast cicada dates

Cold-hardiness zone map, heat zone map and fruit chill hour requirements

 

Our pond iced over.
Photo Ezra Freeman

I was alarmed to hear on NPR that the USDA had issued a new map of winter-hardiness zones. It seemed so recent that we got an update! Relax! (Sort of!) It’s the same 2023 map that I reported on here in November 2023. What is new and worth a visit is the interactive map posted by NPR .

2023 USDA Cold-hardiness zones map

Enter your location and see a map with your zone on the previous 2012 map. Scroll down (it was not immediately obvious to me to do this. . . ) and you can see what zone that area is in now. Scroll further down and you can see the amount the 30-year minimum temperature average has changed since the 2012 map (which used the data from 1976-2005). In my case, Louisa, Virginia has got 3 Fahrenheit degrees warmer in winter on average, than it used to be. Good for keeping some perennials and annuals alive over winter; not so good for fruits requiring a certain number of chill hours, such as apricots.

Our grape rows from the north.
Photo Kathryn Simmons

Fruit and Nut Tree Chill Hours Explained

Apple trees and other fruit and nut trees need cold temperatures to be able to set fruit the following season. Chill hours are the cumulative number of hours during the winter, below a temperature of 45ºF. Nut and fruit trees need a specific number of chill hours each winter to regulate their growth. It is a cumulative total for the whole of the dormant season, whenever they happen. Chill hours are further explained on the Stark Brothers website where there is also this map.Click the link for the ability to zoom in on your location.

Chilling Hours map of the US, for fruit and nut tree growers. MRCC Vegetation Impact Program

Citrus fruits do not need any chill hours. At our farm, we get around 700-800 chill hours each winter. Any tree needing less than 700 will be well served by our winters! Redhaven peaches need 800 – a bit of a gamble. Honeycrisp apples need 800-1000, so they are not for us!

Deke Arndt, director of the National Oceanic and Atmospheric Administration’s National Centers for Environmental Information says that winters are warming at a faster pace than other seasons.

Also, an increase in the quantity and quality of data collected at weather stations across the nation in recent years has helped to increase the overall accuracy of temperature readings. The 2021 data are more accurate than the 2012 data, so the difference (change) over that time is a bit uncertain.

Immature frosty cabbage. Photo Lori Katz

Scroll down the NPR page further, and after a reminder that your zone measurement is an average of the coldest yearly temperature in your area over the past 30 years, you can see a scatter chart of the actual coldest temperature each year from 1991 to 2020. The coldest here was -13ºF in 1996. In that same period, seven winters have had a minimum that was warmer than 10ºF. When you average those coldest nights in each of the 30 years, the average comes out at 4F here. That is, the average coldest night over 30 years was 4ºF.

Scrolling down further we see that puts us in zone 7a, where the average lowest temperature each winter is in the range 0ºF-5ºF. Next comes a reminder that this is only useful for plants that have to survive the winter.

The site focuses on ornamental perennials: You plant them once and they come back after each winter if they’re given the right environment to survive. Think things like trees, shrubs and woody plants. Hydrangeas, Azaleas and Lavender can survive our winters. The Windmill Palm grows in zones 7-11. It might survive here. But, anyway, I’m more interested in vegetables.

A stormy winter day, garlic, rowcovered spinach beds and our hoophouse.
Photo Wren Vile

However, it’s also true that the lowest winter temperature affects annuals that are overwintered to produce spring vegetable crops. Combine the information about your winter-hardiness zone with my Winter-Kill Temperatures of Cold-Hardy Crops list to see what vegetables it is worthwhile keeping in your garden over winter, and which ones will probably survive with rowcover. And which would need a hoophouse or greenhouse to survive.

On its own, your cold-hardiness zone can’t tell you what to grow in your area. For example, parts of Juneau, Alaska; Boston, Mass.; and Santa Fe, N.M are all in USDA’s Zone 7a, as are we in Louisa, VA.

Juneau has relatively temperate winters that are extremely wet, averaging over 80″ snow a year. Santa Fe is extremely dry, with much hotter summers than Juneau. Boston has temperate winters and temperate summers. It gets rain, but not nearly enough for Juneau’s rainforest plants to thrive. It gets heat in the summer, but is colder and wetter in the winter, preventing desert plants like cactuses and other succulents from thriving.

Because all these three cities rarely get below 0ºF each winter, they are all classified as zone 7a.

Vates kale with a freeze-killed center January 19 2018.
Photo Pam Dawling

Here are some things to keep in mind about winter-hardiness zones:

  • Your winter temperature can still dip below your hardiness zone. Remember, your zone is a measure of the average coldest night in 30 years. Some years are above average, others are colder!! Even much colder! In 2014, the temperature in St Louis (zone 7a) dipped three half zones below St. Louis’ hardiness zone, to -10º F. So be alert to the threat of extreme cold snaps. And find a way to keep your plants warmer until the snap passes.
  • The hardiness map says nothing about the frequency of extreme cold weather. A plant or an animal can survive an occasional short dip to a temperature much colder than usual. But an extended period of very cold weather is more deathly.
  • Sweet potatoes in storage. An ideal crop for winter meals, as they store at room temperature for a long time, maybe seven or eight months.
    Photo Pam Dawling
  • The hardiness map can’t tell you if your plants will survive the summer.  I have had people ask me what zone sweet potatoes can grow in. My reply is that winter-hardiness zones will not affect sweet potatoes, because they are not out there in the soil in the winter! They are in your basement or a root cellar or a storage room, above 55ºF.
  • AHS Heat Zone Map 1997
  • For thinking about summer temperatures, consult the 1997 American Horticultural Society heat zone map that measured the average number of times per year that the temperature of an area exceeds 86ºF. The heat zone map is on the NPR site, if you scroll far enough. With 60-90 days a year with a high temperature above 86ºF, Louisa, VA is in heat zone 7 of the 12 created. I hope an update of this map comes soon.
  • If your winter-hardiness zone has changed, you could plant some new things, or leave plants such as figs, or spinach, that you previously wrapped each winter, unwrapped.
  • Warm microclimates such as containers on paved surfaces or near brick buildings absorb a lot of radiant heat during the day and hold it into the night.
  • Remember the cold-hardiness zone calculations are using the past 30 years’ data. If you notice temperatures are continuing to climb, year after year, you could experiment with less-hardy plants from the half-zone warmer than yours.
  • Your local Extension Service may be able to help with more local information.

Weed of the Month for May: Galinsoga

People in early spring weeding spinach that has been hooped and covered overwinter.
Photo Wren Vile

This is the first of my new monthly series of posts. All about weeds.

Sustainable (or Ecological) Weed Management: A Holistic Approach to Organic Weed Management

In the early days of organic farming, maximum use was made of frequent cultivation to kill weeds. Now we know that too-frequent cultivation risks causing soil erosion, and that each tilling or deep hoeing stirs air into the soil and leads to a burning-up of organic matter. The practice of sustainable weed management is about effectiveness – including removing weeds at their most vulnerable stage, or at the last minute before the seed pods explode – and ignoring weeds while they are doing little damage. Work smarter, not harder!

Start with restoring and maintaining balance in the ecosystem. Develop strategies for preventing weeds and for controlling the ones that pop up anyway. An obvious point is to avoid adding new kinds of weeds to any part of your fields. Remove the hitch-hikers from your socks out on the driveway, not when you notice them as you squat to transplant onions! We use our driveway as a convenient place to “roadkill” particularly bad weeds by letting them die in the sun. Beware of Trojan plant swaps!

Weeding in early June. Photo Lori Katz

Weeds are not a monolithic enemy, but a diverse cast of characters. Applying biological principles is not an attitude of war, but more like ju-jitsu, using the weaknesses of the weeds to contribute to their downfall. Develop an understanding of weeds and the different types: annual/perennial; stationary perennials/invasive perennials; cool weather/warm weather; quick-maturing/slow-maturing; and what Chuck Mohler referred to as “Big Bang” versus “Dribblers”. In this monthly blogpost series, we’ll meet various types of weeds, and develop a broader understanding of how and when to tackle each kind.

One factor to consider is how vulnerable the crop is to damage from that weed at that time. Weeds that germinate at the same time as a vegetable crop usually do not really affect the crop’s growth until they become large enough to begin competing for moisture and nutrients. These early weeds have the greatest potential for reducing crop yields if allowed to grow unchecked. We need to cultivate or otherwise control weeds before this 2- to 3-week grace period is over.

Weedy sweet corn. ideally, we would have cultivated two weeks and four weeks after sowing. Photo Bridget Aleshire

The critical period for weed control for the crop is the interval from the end of the initial grace period until the end of the minimum weed-free period, which is approximately the first third to one half of the crop’s life. For vigorous crops like tomato, squash and transplanted brassicas this is four to six weeks; less vigorous crops like onion or carrot need weed-free conditions for eight weeks or more. During that period it is essential to control weeds to prevent loss of yield.

Weeds that emerge later have less effect, and ones that emerge quite late in the crop cycle no longer affect the yield of that crop, although there are long-term reasons for removing weeds to improve future crops.

Know Your Weeds

Lettuce with weeds, easily hoed. Photo Bridget Aleshire

Learn to identify the major weeds on your farm, and any minor ones that suggest trouble later. Observe and research. Start a Weed Log with a page for each weed. Add information about your quarry’s likes and dislikes, habits and possible weak spots. Find out how long the seeds can remain viable under various conditions, and whether there are any dormancy requirements. Note down when it emerges, how soon it forms viable seed (if an annual), when the roots are easiest and hardest to remove from the soil (if a perennial), what time of year it predominates, which plots and which crops have the worst trouble with this weed. Monitor regularly throughout the year, each year. Look back over your records and see if anything you did or didn’t do seems to have made the problem worse or better.

Next think about any vulnerable points in the weed’s growth habit, life cycle, or responses to crops or weather that could provide opportunities for prevention or control. List some promising management options. Try them, record your results, decide what to continue or what to try next.

Most weeds respond well to nutrients, especially nitrogen. If you give corn too much nitrogen, even as compost, the corn productivity will max out and the weeds will use the remaining nutrients. Some crops, like carrots and onions never cast much shade at any point of their growth, so that sun-loving weeds like purslane are more likely to thrive there, but not be a problem for crops which rapidly form canopies that shade the ground.

Galinsoga – a fast growing, fast-seeding weed of cultivated soil.
Photo Wren Vile

Galinsoga

This month’s Weed Character is galinsoga, a “Seed Dribbler”, that matures seed while still quite small plants, sheds some, makes some more, and can carry on for a long seed-shedding season.

Encouraging information is that a constant percentage of the seeds that are still left from one year’s shedding dies each year. This varies widely among species – for lambsquarters it’s 31% per year in cultivated soil (only 8% in uncultivated soil). The number of seeds declines rapidly at first, but a few seeds persist for a long time.

While seeds survive better deeper in the soil, they don’t germinate better down there. Larger seeds can germinate at deeper levels than small seeds. If you are trying to bury seeds deep, use inversion tillage, don’t rely on rotavating, as seeds somehow manage to stay near the surface with rotary tilling. Chuck Mohler, author of the excellent book Manage Weeds on Your Farm, has tested this out with colored plastic beads.

We have two kinds of galinsoga: narrow-leaved and hairy. Both behave the same way. They thrive in highly fertile, freshly tilled soil, just the same as you hope your vegetable seeds will. Mostly we think about how to get rid of galinsoga (prompt hoeing or other cultivation before it flowers), or stop it germinating in the first place (mulches). Its flowers attract beneficial insects such as hoverflies, and it can be eaten by humans and livestock. Young leaves can be used in a soup or in mixed dishes. It doesn’t have a strong flavor. The plants contain flavonoids and phenolic compounds, and it has been found to have antioxidant and anti-inflammatory properties. Extracts from hairy galinsoga can coagulate blood. It is an alternate host for certain nematodes and over twenty insect pests. Hairy galinsoga is thought to have originated in Central and South America, and has become naturalized in North America and other temperate and tropical regions.

Galinsoga is a summer annual that belongs to the sunflower family (Asteraceae) and can invade vegetable gardens with dense infestations that crowd out crop plants. The secrets of galinsoga’s success are that its seeds germinate immediately they reach the soil (no dormancy period), it grows very fast, shading out other plants, it sets seed in as few as 30–40 days after emergence, and continues shedding seed as long as it is growing. It also has the knack of re-rooting if pulled and laid on the surface of the bed, if there is any moisture in the soil. Large plants seem able to transfer the water in their cells to their roots, helping re-rooting happen. Seed that is shed early in the year is capable of growing a mature plant very quickly. There can be multiple generations in one warm season. Fortunately, the seeds are short-lived, and have to be in the top 0.25″ (6mm) of the soil to germinate.

Hoe weeds while they are small and you’ll be rid of those with short-lived seeds in a few years. Galinsoga and Outredgeous lettuce.
Photo Pam Dawling

Galinsoga Identification

Hairy galinsoga (Galinsoga quadriradiata), has profuse hairs on stems and leaves. Narrow-leaved galinsoga ( Galinsoga parvifolia), is very similar, except it is not hairy and it has narrower leaves. Leaves are oval with serrated margins and distinct petioles. They are arranged opposite each other on the stems. The flowers have densely packed yellow disc florets and five tiny white ray florets, each with three scalloped teeth at the end. Seeds of hairy galinsoga germinate between 54°F-86°F (12°C-30°C) with an optimum temperature requirement of 68°F-75°F (20°C-24°C). Most of the seed germination occurs from May to June, after the last frost. It flowers abundantly from about late-May until late fall here in central Virginia. Fallen seeds can germinate immediately due to the absence of dormancy requirement. Take advantage of this phenomenon to eradicate hairy galinsoga from an infested field in three to four years by careful management.

Controls for Galinsoga

Prevention of Weed Germination

Hoeing or mechanical cultivation is effective if carried out repeatedly during the early stages of growth (before flowering). Mulches, such as thick (6-mil) black plastic, or straw, hay, leaves, woodchips over cardboard or newspaper, are effective to control galinsoga in small gardens if applied immediately after planting the crop and before the galinsoga germinates.  Tarping is the equivalent solution for larger areas.

Reduction of Weed Seeding

Grazing, or the mechanical equivalent, mowing, will take care of galinsoga in places you are not currently growing a crop. This weed is not usually found in lawns. It has no resistance to frost. Livestock will happily graze it.

Reduction of Viability of Seeds

Most weed emergence happens within two years of the seeds being shed. Not all seeds that are produced will ever get to germinate (I was very pleased to learn that seeds have many ways of not succeeding!) You can help reduce their chances, by mowing crops immediately after harvest, (to prevent more weed seed formation); then wait before tilling to allow time for seed predators to eat weed seeds that already produced. Seeds lying on or near the soil surface are more likely to deteriorate or become food for seed predators than buried seeds, so delaying tillage generally reduces the number of seeds added to the long-term seed bank. (Short-term, they may germinate!)

If they do not get eaten, dry out or rot, seeds on top of the soil are more likely to germinate than are most buried seeds, and small, short-lived seeds of weeds which have no dormancy period, such as galinsoga, will almost all die within a year or two if they are buried a few inches.

Putting it Together

Strategies include

  1. Inversion tillage such as moldboard plowing (seeds will die off deep in the soil within a year or so.)
  2. Mulching – the seeds will not germinate or be able to grow through the mulch, and will be dead by next year. Be sure to rotate the mulched crops around the farm, so that the benefits are not confined to one section;
  3. Grazing with small livestock, or harvesting galinsoga for human consumption, or mowing: especially mow as soon as the food crops are finished, if you cannot till right away.
  4. Tarping (mow first);
  5. No-till cover crops, with summer crops transplanted into the dying mulch;
  6. Stale seed bed techniques, including flaming;
  7. Plant flowers that attract beneficial insects, particularly seed-eating insects, and birds.
Front cover of manage Weeds on your Farm

Resources on Weeds

Lettuce Growing Tips

 

Our first outdoor lettuce bed in May.
Photo Wren Vile

 Lettuce growing conditions – germination

  • Lettuce seed needs light to germinate – don’t sow too deep: 1/4″–1/2″ (6–10 mm) is ideal.
  • Minimum soil temperature for germination is 35°F (1.6°C).
  • Optimum temperature range for germination is 68°F–80°F (20°C–27°C). I have a table of optimum soil temperatures for germination in my book The Year-Round Hoophouse
  • Germination takes 15 days at 41°F (5°C), 7 days at 50°F (10°C), 3 at 68°F (20°C), only 2 days at 77°F (25°C)
  • Germination takes 3 days at 86°F (30°C), but will not occur reliably at temperatures hotter than that.
  • A soil thermometer soon pays for itself and saves lost crops and frustration.

Lettuce crop requirements

  • Free-draining soil, high organic matter, pH 6.0–7.0.
  • Fertile soil with good tilth will help roots grow.
  • Don’t overdo the nitrogen – encourages E. coli.
  • Keep lettuce growing quickly for good flavor – plenty of water throughout its growth.
  • Ideal growing temperatures 60°F–65°F (15°C–18°C).
  • Some growth whenever the temperature tops 40°F (4.5°C).
  • Cultivate regularly and shallowly to remove weeds.
Lettuce nursery bed with soil thermometer behind the sheep
Photo by Bridget Aleshire

Sowing lettuce for transplanting

  • You can sow in cell-packs or plug flats, 3 seeds per 1″–2″ (2.5–6 cm) cell, later reducing to 1 seedling with scissors.
  • If suitable germination space is limited, sow seed in a small flat or shallow pot, then spot the tiny seedlings into bigger flats or 606-cell packs (2″ × 2″, 5 × 5.6 cm) to grow on before planting out.
  • Can use an outdoor nursery bed from mid-April to October, rather than flats. Transplant the bare-root plants directly from the seedbed.
  • But in very hot weather, indoor sowings might give more reliable germination.

Transplanting lettuce

  • Harden off before transplanting.
  • Transplant lettuce seedlings at 4–6 true leaves, 3–6 weeks of age depending on how fast they are growing.
  • Handle transplants only by their leaves or the root ball—try not to touch the roots or stem. This minimizes the damage from your hands.
  • 8″–12″ (20–30 cm) spacing for full-sized heads. Close spacing lets foliage cover the bed completely, creating a cooler microclimate.

Lettuce Types

  1. Iceberg (crisphead) lettuces have little nutritional value. They have no frost tolerance because of their high water content. 75-100 days from direct seeding.

    Buttercrunch Bibb lettuce. Photo Kathleen Slattery
  2. Butterheads (bibbs) have very tender leaves, but have shorter shelf-life than romaines and leaf varieties. 60-75 days from direct seeding.
  3. Romaine (cos) lettuces are upright, often very crisp and flavorful. They have more vitamins than other lettuce types. &0 days or more from direct seeding.

    Green Forest romaine lettuce.
    Photo Pam Dawling
  4. Leaf lettuces include the familiar oak-leaf types, and frilly ones. You can harvest individual outer leaves or cut the whole plant. 45-60 days from direct seeding.
  5. Batavian lettuces (summer crisp or French crisp) are tasty, thick-leafed varieties that have great heat and cold tolerance. Although sometimes classified with icebergs as crisphead types, they are very different.
  6. Multileaf lettuces – familiar Tango, Panisse and Oscarde, and the newer Salanova, Multileaf and Eazyleaf brands. They are bred for uniformly small leaves, with more texture, loft and flavor than baby mixes and faster harvesting. Transplanted 6″–8″ (15-20 cm) apart they produce 40% more than baby leaf mixes. The full-size plant can be harvested as a head, providing a collection of bite-sized leaves. Or just one side (or the outer leaves) of the plant can be cut and the plant will regrow for future harvests. Growing multileaf heads takes 55 days, compared to 30 days for baby lettuce. For the most harvest, pick the outer leaves and let the middle regrow.

    Ezrilla Tango-type one-cut multileaf type lettuce
    Photo High Mowing Seeds
  7. Baby lettuce mix, aka mesclun, salad mix, spring mix and misticanza. Some mixes include other greens. 21 days from seeding in mild weather. Up to 63 days in cold weather.

Lettuce varieties for every time of year

We used to reckon on five lettuce seasons, but with climate change, our Early Spring shrank and became encompassed in our Spring, so now we have 4 lettuce seasons, and we always sow 4 diverse varieties:

  • Spring (Jan 17 – April 22), 8 sowings. Priorities: fast growth, cold tolerance
  • Summer (April 23 – Aug 14), 20 sowings (lots of seed!). Priority: extreme heat tolerance/bolt-resistance. I just sowed our first batch of summer varieties on April 23
  • Fall (Aug 15 – Sept 7), 9 sowings. Priorities: some warmth-tolerance, some cold tolerance
  • Winter (Sept 8 – 24), 9 sowings. Priority: cold-tolerance

Season extension techniques for lettuce in spring

  • Fast-maturing hardy varieties
  • In early spring, use transplants for earlier harvests
  • Warm microclimates (protection from prevailing winds)
  • In spring, warm the soil with black plastic mulch
  • Use rowcover
  • Harvesting early in the year might mean fast production in January and February, or it might mean starting in the fall and overwintering the plants. See my post series Lettuce of the Month, for ideas on varieties and techniques throughout the year. See here for the overview.
A stormy early spring day, garlic, rowcovered beds and our hoophouse.
Photo Wren Vile

Avoid lettuce bolting

Assess your risks and if in doubt, harvest early. Bolting and/or bitterness are more likely with

  • Under-watering,
  • Long days,
  • Mature plants,
  • Poor soil,
  • Crowding,
  • High temperatures,
  • Bolt-resistance generally goes from Leaf types (first to bolt), through Romaines, Butterheads, Bibbs, to Crispheads.
  • Vernalization—once the stems are thicker than 1/4″ (6 mm), if plants suffer 2 weeks of temperatures below 50°F (10°C), followed by a rapid warm-up.
  • Also see What makes vegetable crops bolt and how can I stop it?
You don’t want this! Bolting lettuce outdoors in July
Photo Alexis Yamashita

Keys to year-round lettuce success 

  • Store seed in a cool, dry, dark, mouse proof place.
  • Good soil preparation and high organic matter are important for high quality lettuce, which needs to grow quickly.
  • Location, location, location! We grow lettuce outside from transplants from February to December (harvesting from late April); in a solar-heated greenhouse from September to March (harvesting leaves from November) and in a solar heated hoophouse from October to April (harvesting leaves from November, and whole heads in April). We also sow baby lettuce mix in the hoophouse from October to February, for harvest multiple times from December to April.
  • Use shade cloth on hoops in hot weather
  • Use rowcover in cold weather, or plant in cold frames, greenhouses or hoophouses.

Scheduling lettuce for continuous harvests

  • Lettuce grows faster at some times of year than others, and the time between one sowing and the next needs to vary to balance this.
  • To harvest a new planting every week you need to have sowing gaps of more than 7 days in the spring, 6-7 days in the summer, less in fall.
  • In warm spring weather, baby heads of lettuce or individual leaves can be ready to harvest 4 weeks after transplanting, and full-sized heads 6 weeks after transplanting.
  • In summer, full-size heads can be ready in as little as 3 weeks from transplanting.
  • As temperatures and day-length decrease in the fall, the time to maturity lengthens, and a single day’s difference in sowing date can lead to almost a week’s difference in harvest date.
  • Lettuce for harvest in February will take 2-3 times as long from planting to harvest as that for September harvest.
  • December and January sowings grow very slowly, and early February sowings will almost catch up.
Flats of lettuce transplants in our cold frame in April.
Photo Pam Dawling

Scheduling lettuce January-June

January: sow every 2 weeks

  • Sow indoors in flats in late January for outdoor transplants
  • If you have a greenhouse or hoophouse, transplant there until mid-February
  • Harvest leaf lettuce and baby lettuce mix from protected crops

February: sow every 2 weeks

  • Same as January

March: sow every 13 days, indoors in flats

  • From late March or early April, you could switch to outdoor direct sowing. (We transplant all our lettuce.)
  • Transplant the first 3 sowings outdoors with rowcover
  • Harvest leaf lettuce, baby lettuce mix from a hoophouse; starting late March, harvest leaves from the first outdoor planting

April: Sow every 9 days

  • Transplant the March sowings
  • Harvest whole heads from late April

May: Sow every 8 days

  • Transplant 1 week’s needs each week
  • Harvest outdoor heads

June: Sow every 6 or 5 days, under shadecloth

  • Transplant one week’s needs every 6 days, using shadecloth for the first 2 weeks
  • Harvest outdoor heads

See my post Lettuce All Year in a Changing Climate, which includes links to my slideshow about growing lettuce year round, and our Lettuce Varieties list and Lettuce Log (planting schedule). It also includes keys to succeeding with year-round lettuce (dates for succession planting).

Lettuce bed in May.
Photo Wren Vile

Cover Crops for April: before the last frost.

 

Beds of young buckwheat.
Photo Bridget Aleshire

In January I shared some resources to give the Big Picture of Cover Crops, including a compilation of slides for SARE (Sustainable Agriculture Research and Education) and my slideshow Cover Crops for Vegetable Growers.

In February, I described limiting winter annual weeds by sowing oats in spaces without a cover crop and no planned food crop for 6-10 weeks. Six–ten weeks (depending on your climate) is long enough in early spring to get worthwhile growth from oats before prepping for the food crop. Also see February’s post for the Stale Seedbed and Tarping Techniques.

In March I wrote about some options for cover crops you might be sowing then, and alternatives like a fast-growing hardy leafy vegetable or mixed Eat-All Greens, an idea from Carol Deppe, a great idea if you have more than eight weeks before your main vegetable crop goes in the ground. This is where using transplants really helps increase your total food output. While the frost-tender transplants are growing indoors, you could be growing a “catch crop” outdoors in spaces that didn’t get a winter cover crop. I also talked in the March post about incorporating cover crops. Remember that if you incorporate fresh green cover crops into the soil, you will need to wait two or three weeks to sow, to give the cover crop time to break down in the soil before it can be available for your crop. Especially, wait three weeks after turning under winter rye before sowing, as it produces allelopathic compounds that can inhibit the germination and growth of small seeds. Transplants don’t suffer the same problem.

Potatoes, weeds and standing water. Until the soil drains, the potatoes cannot be hilled, and the weeds here are already large. The yield will be reduced by weeds out-competing the potatoes. Potatoes may be flamed at 6″–12″ (15–30 cm) tall, to kill weeds without damaging the potato plants. After that, flaming is not recommended.
Photo Bridget Aleshire

Once we get to April here, it is too late to successfully grow oats (they will quickly head up after making very little growth). But in climates like ours, we can sow winter wheat or winter rye in April – they will not head up, but will “wimp out” when it gets hot. That is, they will stop growing, so you won’t get a lot of biomass, but you will have some live roots in the soil, holding it together, taking care of the soil microfauna, and discouraging weeds form germinating. One April when our spring-planted potatoes got flooded, we transplanted potato plants to the drier end of the patch and sowed winter rye in the lower end, once the floods had subsided. This kept the soil covered, scavenged the compost we had spread for the potatoes, and was easy to deal with in July when we harvested the potatoes. It was also much more hopeful to look at an area of green cover crop than an area of green weeds!

April is too soon for us to rely on frost-tender cover crops, but by mid-April, we can sow a mix of oats and buckwheat. The oats will protect the buckwheat somewhat from the cold. if the season is warmer than average, the buckwheat will survive and smother weeds, provide pollen and nectar for beneficial insects

Here’s a lovely quote from Barbara Pleasant in SW Virginia:

“It’s April and the soil is warming up and drying out. After loosening a clump of fall-sown wheat with a digging fork, you pull up a marvelous mop of fibrous roots and shake out the soil. What crumb! The soil’s structure is nothing short of amazing! These are the moments an organic gardener lives for.”

Root systems of four grass cover crops at early stages of growth (two months in a greenhouse). From left: annual ryegrass, barley, triticale (winter biennials) and sorghum-sudangrass (summer annual). Photos by Joseph Amsili. From SARE

Depending on the stage of the year where you are, you could revisit any of the earlier posts. Here are links for each of the cover crop posts in the past year.

May: Buckwheat and Other Summer Cover Crops

June: Sunn Hemp, Soybeans, Southern Peas, and Partridge Pea, Senna Ligustrina

July: Millets and Sorghum-Sudangrass (Sudex)

August: Oats, Barley and Other Winter-Killed Cover Crops

September: Winter Wheat and Crimson Clover

October: Winter Wheat and Austrian Winter Peas

November: Winter Rye (with Austrian Winter Peas early in November)

December: Planning Winter Cover Crops

January: The Big Picture, Ponder and Plan Your Cover Crop Strategies for the Coming Year

February: Oats if you have a 6–10 Week Gap

March: Sowing Options and Incorporating Cover Crops

Perennial and Native Cover Crops

I attended a workshop at the VABF-SFOP Summit on cover crops led by Cerruti R2 Hooks, Veronica Yurchak, from the Department of Entomology, University of Maryland, and Hanna Kahl of UC Davis. The UMD Eastern Shore IPM Center has lots of useful programs and publications. They focus on the most important pest problems and make science-based information available to everyone who contends with pests. This workshop discussed how cover crops influence weeds, plant diseases and insects. Cover crops can smother weeds, augment weed seed predators (lifeforms that eat weed seeds), create a weed-suppressive soil microbe community, release allelochemicals that are toxic to weed seeds, release nitrogen into the crop germination zone, boosting crop growth, cool the soil and compete with weeds for resources.

Cover crops can decrease crop diseases by increasing the diversity of soil organisms, making soil more disease-suppressive; releasing compounds unfavorable to disease organisms; trigger plant immune responses; increase the number of beneficial organisms and forma physical barrier that reduces splash-back from the oil. A nice example is that sunn hemp interplanted in squash rows can cause aphids carrying virus particles in their mouth parts to drop them in the sunn hemp where they do no harm.

Sunn hemp at Nourishing Acres Farm.
Photo Pam Dawling

Cover crops can repel some insects and nematodes, as well as providing habitat, nutrients and protection from predators for the beneficial insects. This can help augment the population of beneficial insects. Cover crops can also act as trap crops for problem insects by being more attractive to them than the crop plants. Cover crops can also cause microclimate change within the crop, for example by acting as a windbreak.

The speaker gave examples with red clover, a short-lived perennial, sown in the previous fall between cucumber rows that were planted in spring. The population of striped cucumber beetles was lower, while populations of beneficials such as big-eyed bugs, minute pirate bugs and ladybugs were increased.

In November 2023, at the Carolina Farm Stewardship Conference, I went to an engaging workshop called On-Farm Cover Crops Research in the Carolinas by Justin Duncan from NCAT/ATTRA, Jason Lindsay from the Southeastern African American Farmers’ Organic Network, and Steve McAllan. See his YouTube  Cover Crops for Hot & Humid Regions. At the workshop, Justin Duncan explained Push-Pull Trap Cropping, invented in Kenya, combining a companion plant that repels a pest with a trap crop nearby that attracts it, making pest control easier.

Pigeon Pea as cover crop. Photo https://conservationist.wordpress.com/2008/11/03/pigeon-pea-as-cover-crop/

He advocated for pigeon peas (Cajanus Cajan) as a cover crop for warm droughty climates, that will also keep the soil cooler. When mean temperatures rise 1 Celsius degree, soils in warm areas burn up 10% of their OM, and cool areas lose 3%. Loss of water leads to loss of OM, leading to more water loss. Hot humid areas need twice as much OM as cooler ones to maintain fertility. No-till can cut the loss of OM by half compared to conventional tillage. Other cover crops Justin Duncan recommended include Perennial Peanut, good in orchards, Chamaecrista rotundifolia (round-leaved cassia) and Scarlet Runner beans. Cover crops are a way of growing Organic Matter in place.

Patrick Johnson, RVA Permaculture. Photo https://rvapermaculture.com/about-us/

Patrick Johnson, a Virginia permaculturist, also gave a presentation on native cover crops. See his Proposal and Project Overview:  https://projects.sare.org/sare_project/fs22-345/

And read the Feb 2024 SARE report Using a Native Legume as a Cover Crop for Soil and Vegetable Production Benefits in Small Scale Vegetable Production.

No-Till Cover Crops

I have not covered these yet, and don’t have much personal experience, apart from our one-year-in-ten growing of paste tomatoes in a mow-killed rye, hairy vetch and Austrian winter peas dying mulch. I’ll make a separate post for next week about combining cover crops and no-till methods.

Cover Crop Training Videos from SARE

See SARE for a series of ten training videos.

Weeds Next

For my next annual series of blogposts, starting at the beginning of May, I will cover Weeds of the Month.

Cover Crops for March: Sowing Options and Incorporating Cover Crops

In March, where we undersowed clovers in the broccoli patch in August, the old broccoli trunks are surrounded by a sea of green clover.
Photo by Kathryn Simmons

In December I wrote about Cover Crop Planning for Next Year, including 5 steps of cover crop planning for all opportunities. I have a slideshow Crop Rotations for Vegetables and Cover Crops, which I find to my surprise that I haven’t posted here since my 2014 version.

Here it is now

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In January I shared some resources to give the Big Picture of Cover Crops, including a compilation of slides for SARE (Sustainable Agriculture Research and Education) and my slideshow Cover Crops for Vegetable Growers.

In February, I described limiting winter annual weeds by sowing oats in spaces without a cover crop and no planned food crop for 6-10 weeks. Six–ten weeks (depending on your climate) is long enough in early spring to get worthwhile growth from oats before prepping for the food crop.

This month I will include some options for cover crops you might sow in March (in central Virginia and similar climates), and then talk about incorporating cover crops, which surely you will be doing this month!

Cover crops to sow in March, and other options

Purple stemmed mizuna. Mizuna and other frilly mustards are fast-growing crops, attractive to the eye and the palate.
Photo Pam Dawling

Depending on the stage of the year where you are, you could revisit any of those posts.

  • In early March the oats plan still works for us.
  • In early spring, the air and the soil are cold, and sowing a fast-growing vegetable crop will not be successful with a gap of less than eight weeks. Crops take too long to grow at this time of year.
  • If you have more than eight weeks you could try those fast-growing vegetables: kale, spinach, Tokyo bekana, radishes, chard, lots of salad crops, senposai, mizuna, tatsoi, land cress. Or try Eat-All Greens, an idea from Carol Deppe. Patches of carefully chosen cooking greens are sown in a small patch. When it reaches 12″ (30 cm) tall, Carol cuts the top 9″ (23 cm) off for cooking, leaving the tough-stemmed lower part, perhaps for a second cut, or to return to the soil.
  • In late March or April in climates like ours, we can sow winter wheat or winter rye – they will not head up, but will “wimp out” when it gets hot. That is, they will stop growing, so you won’t get a lot of biomass, but you will have some live roots in the soil, holding it together and taking care of the soil microfauna, and discouraging weeds form germinating. One year when our spring-planted potatoes got flooded, we transplanted potato plants to the drier end of the patch and sowed winter rye in the lower end, once the floods had subsided. This kept the soil covered, scavenged the compost we had spread for the potatoes, and was easy to deal with in July when we harvested the potatoes. It was also much more hopeful; to look at an area of green cover crop than an area of green weeds!
  • Once we get to March 31 here, it is too late in the year for us to sow oats (they will quickly head up after making very little growth) and too soon to rely on frost-tender cover crops. See the section in February’s post on the Stale Seedbed and Tarping Techniques.

    Tarping beds to kill weeds.
    Photo Cornell Small Farms Unit
  • By mid-April, it is an option to sow a mix of oats and buckwheat. The oats will protect the buckwheat somewhat from the cold. I’ll come back to that idea next month.

Incorporating cover crops, or not

See Barbara Pleasant: How to Take Cover Crops Down. Gardeners working with small tools can start by mowing their live cover crops, grazing poultry on them, or scything them and hauling them aside to use later for mulch. On a very small scale, you can pull your cover crop plants, although I think it is valuable to leave the roots in the soil. On a larger scale, you can graze larger animals, or cut the cover crop down. If the cover crop was winter-killed, the stems will easily disintegrate, so you can skip the cutting down part of these instructions.

If you plan to incorporate the cover crop, choose a mowing method that cuts the plants into small pieces, making them easier and faster to incorporate. On a small scale, this could be a weed whip or a lawn mower; on a larger scale a bush hog. If you plan to use the cover crop for mulch, cut it in a way that leaves the stems as whole as possible. On a small scale this means a sickle or scythe, on a bigger scale, the kind of machinery you might use to cut hay.

Cover crop of rye, vetch and crimson clover in March.
Photo Kathryn Simmons
Rows of Roma paste tomatoes, some on bioplastic, some no-till. Credit Bridget Aleshire

After getting the cover crop down, you could tarp for a minimum of three weeks (allow for more), or you could work the residue into the soil, with a chopping hoe or by digging it in, or using a walk-behind two-wheel tractor such as BCS with a rototiller or a power harrow, or a four-wheel tractor and discs. Cornell has posted a webinar Pairing Tarping with Cover Crops, by Brian Marr.

If you incorporate the cover crop into the soil green, you will also need to wait two or three weeks (or more in early spring) to plant or sow, to give the cover crop time to break down in the soil before it can be available for your crop.

Winter rye produces allelopathic substances that can temporarily inhibit the germination and growth of small seeds. Wait three weeks after turning under before sowing. Transplants don’t suffer the same problem. Oats, wheat, and other cereals also have this tendency, but to a much smaller degree, usually small enough to ignore. Sorghum-Sudan grass hybrid incorporated fresh in the soil hinders the growth of tomatoes, lettuce, and broccoli, but that’s a summer cover crop you won’t need to think about for several months.

I still haven’t got to my Conference notes on cover crop workshops, 2023-2024, but this is enough for one post!