Okra Planting Time

Young okra plants.
Photo Wren Vile

We’ve reached mid-May, the time of year to transplant our okra. Okra is a tropical annual in the mallow family, and is widely adapted where the frost-free season is long enough. Okra is heat- and drought-tolerant and has few serious pests or diseases. Those in hot climates will need to deal with its exuberant growth in mid-summer. Those in cold climates should choose fast-maturing varieties and transplant into black plastic. In areas with cold nights, okra can only be grown in a hoophouse.

Okra Varieties

We like Cow Horn okra from Southern Exposure Seed Exchange, which gives good yields and sturdy plants in our zone 7a climate. It is one of a few varieties that can grow relatively large pods without their becoming tough. We are sometimes not good at finding all the pods when harvesting, so it is an advantage to us if they are still good to eat when bigger than normal. SESE has an Okra Growing Guide.

High-yielding varieties include Cow Horn (55 days), Jade (55 days), Cajun Jewel (50 days).

Spineless (easy to harvest) varieties include Clemson Spineless (56 days), and Evertender (50 days). Red-podded varieties include Burmese (58 days), a high-yielding dwarf heirloom, and Red Burgundy (49 days), reported to do well in “cooler” areas, although it will not do much until day time temperatures reach 80°F (27°C).

Close up of Cow Horn okra pods.
Photo Kathryn Simmons

Crop Requirements and Yield

Okra does best in well-drained, fertile, loamy soils with high organic matter. Wet clay soils can drown the plants. It grows best with a pH between 6.5 and 7.0, although as high as 7.6 is still OK.

5 gm sows 50’ (15 m) at 6” (15 cm) spacing. Average yields are about 50-100 lb/100’ (7.6-15 kg/10 m). We grow 90’ (27 m) for 100 people, which provides enough for some pickling too.      

Sowing okra

According to Rodale’s 600 Answers, germination speed can be improved by freezing the seed overnight, then soaking in hot water for ½-1 hour before sowing. It needs to be warm enough to get your seed germinated: you can soak the seed for 8 hours in water at 88°F (31°C).

When we direct sow, we “station-sow” – we put three seeds ½-1” (1-2.5 cm) deep at each spot where we want a plant to grow. We do this on May 1, with rowcover, as this is around our last frost date, and we want to avoid disasters! Direct sow once the soil temperature averages 65°F (20°C), 3-4 weeks after last frost.

When seedlings have 3-4 leaves, we thin to the strongest seedling. Okra is sturdier if direct sown, rather than transplanted, but you work with the climate you’ve got!

Transplanting okra

Okra seedlings in a Winstrip 50-cell tray.
Photo Pam Dawling

Usually we transplant, especially if we are intercropping. For transplants we sow April 15, using soil blocks or Winstrip 50-cell flats. I was amazed to learn that at 6″ (15 cm) tall, plants could have taproots three times as long! At full maturity, the tap root could be 4½ ft (1.4 m).  To avoid stunting the taproot, get the small plants in the ground as soon as you can, carefully.

We transplant 3-4 week old starts – a plant with 3 or 4 leaves is ideal – at 18” (45 cm) spacing in a single row down the middle of a bed. We transplant May 11, 10 days later than the direct-sowing date. In the past we used wider in-row spacing, but found we could get a higher yield with the “hedge-like” closer spacing.

Some growers plant as close as 6” (15 cm) in the row, with 5’ (1.5m) between rows, or plant double rows with 12” (30 cm) between plants, and wider spacing between the beds. Thick planting requires very fertile soil, and risks diseases from poor air circulation. Wide spacing can lead to heavily branched plants, and more pods per plant, but not necessarily more pods for a given area. It may lead to a later start to the harvest, as flowering is delayed while the plant grows bigger.

Burmese okra flower.
Photo by Raddysh Acorn

Intercropping Okra

Okra is slow-growing until hot weather arrives. We sometimes take advantage of this and its upright growth habit to transplant okra into a bed of early cabbage. We transplant cabbage in two rows along a 4’ (1.2 m) bed on March 10 and the okra in a single row down the middle on May 11. We mulch the cabbage, which has the disadvantage for the okra, of cooling the soil, so don’t try this if direct sowing! At first the cabbages are relatively small, and the okra uses the open space in the middle of the bed. As the plants grow, we remove outer leaves of the cabbage that might overshadow the okra. Finally, we harvest the cabbage and leave the okra to grow to full size. This method saves space, and efficiently uses our time to help two crops with one weeding.

Okra plants can be huge by September!
Photo Pam Dawling

This post is part of what I have written about okra in my book Sustainable Market Farming. Buy the book to read the rest, including crop rotations, pests and diseases, harvesting and post-harvest care of okra.

Pickled okra, garlic scapes and beets.
Photo Bridget Aleshire

The Whole Okra

See my review of Chris Smith’s book The Whole Okra. Chris has grown 125 varieties of okra, and still counting, and cooked it in many different recipes. His book includes using the oil from the seeds, eating the leaves; making okra-stem drinking straws, okra seed tempeh, okra marshmallow delights; okra history and geography, medical and industrial uses and so much more. Here are instructions for freezing the sudden glut of okra that often arrives at some point in the summer, pickling (both by fermenting and with vinegar), drying (best when strung on dental floss). Best of all are the okra chips. Chris has a video of taste testing on YouTube, https://www.youtube.com/watch?v=sAy0pouxlME

Fruit for May

Flowers on a two-year-old strawberry plant.
Photo Kathryn Simmons

This is the first of my new monthly series, about small fruits that can be grown sustainably in a mid-Atlantic climate. I’ll talk about planting, pruning, harvesting and care of the plants, according to the season. I’ll give links to useful publications. I’ll have a focus fruit, and then more about others that need attention during the month. We do grow apples and pears, and some other tree fruit, but I’m not writing about those as I don’t have much recent experience.

Strawberries are the focus fruit for May

May is the month in our climate, to harvest and weed strawberries. Actually weeding strawberries in bare soil is a job that needs doing once a month from February to November here! We don’t have any strawberries in our gardens this year. Once upon a time, we grew matted rows, where you keep the same bed in production for multiple years, removing the oldest plants to make space for younger more vigorous plants. Weeds were our downfall. Once you let weeds seed in a strawberry bed, you have lost the battle. In our climate, we have cold-weather weeds and warm weather weeds. Semi-permanent strawberry beds get them all. I wouldn’t choose this method again.

See ATTRA Strawberries: Organic Production available free online, for a wealth of information. Updated April 2021.

Strawberries need a lot of weeding if grown on bare soil.
Photo Twin Oaks Community (Renee)

Harvesting strawberries

I recommend harvesting three days a week, in the mornings, once the dew has dried, to avoid spreading fungal diseases. Use shallow containers, although strawberries don’t crush as easily as raspberries. Turn each ripe-looking strawberry over to make sure it’s ripe underneath too. We will harvest with white tips, but not green. Commercial strawberries that will travel long distance are harvested ¼ green and arrive very red, but with not much flavor.

Nip through the stem of the fruit with your nails and set the fruit in the container. Also, now or preferably separately, collect up any moldy or bird-bitten fruits to compost. It’s better not to handle healthy plants after moldy fruit, but if you have dry weather and not many moldy ones, it’s very tempting to remove them as you go. When “Mouseberry”, our nickname for Botrytis grey mold, is only a minor problem, we just hurl each one as far from the strawberry bed as we can, rather than collect them up.

Unblemished strawberries can be stored for several days in the refrigerator. Do not wash before refrigerating, as this leads to rot. If you are planning to process lots of strawberries for drying, jam, juice or other value-added products, I recommend finding a simple little tool, a pair of round-ended tweezers about 2” (5 cm) long and ½” (1 cm) across. You can twist our the green tops quickly with minimal wastage.

A dormant bare root strawberry plant.
Photo Kathryn Simmons

When to plant strawberries

In case you don’t yet have strawberries, and now wish you did, here are some considerations about when to plant. Many gardening books are written in more northerly climates, where bare-root transplants are set out in early spring. But then it is necessary to pinch off the flowers the first year. And still weed once a month! We found it better here to plan for September planting of runners we had potted up in July, leaving them attached to their mother plants until time to make the new bed. They are less likely to die if still attached to the well-rooted mother plant. Fall-planted strawberries do not need to have the flowers removed in their first spring. It is not easy to find bare-root transplants to buy in the fall.

In Virginia, many commercial growers plant new strawberries on plastic mulch every year, buying in plugs. The costs are covered by the high price that strawberries bring in when sold. We were not selling, but feeding our intentional community. This means that produce that would get high prices doesn’t repay us for the time spent. We need nutrients for a well-balanced diet, not fancy stuff. This issue also came up for us when we grew ginger in our hoophouse. Tasty and enjoyable, but not lots of food for the space and time.

Newly prepared strawberry beds with landscape fabric.
Photo Wren Vile

As a balance, we settled on keeping two beds (one early variety, one late) for two years each, using landscape fabric with holes melted in it. Each year we would make 1 new patch, till in the older one after 2 harvests. Some years we bought plants, and we also figured out a good propagation method, which gave us plants when we needed them, without too much money or labor. We had backup plans in case we failed to propagate enough replacements.

In early June we’d prepare new beds if going for bare-root plants; after fruiting we’d dismantle the two-year-old bed, renovate the one-year-old bed, and in early July prepare the new bed if using plugs. We did the propagation of our own plugs during July, setting up a misting tent. We planted the new plugs in early August. I’ll go into detail about these tasks when we get to that time of year.

Patented varieties

Some varieties are patented and it is illegal to propagate your own without permission from the patent holder. It’s most illegal to sell plants you have propagated from a patented variety. Technically, it is also illegal to propagate for you own use, and even to let strawberry runners root themselves beside a mother plant. Not all varieties are patented. Cornell has a page Patent Status of Select Strawberry Varieties with info for varieties that do well in NY State. It includes when patents expire. StrawberryPlants.org has a lot of information, including an interactive variety list. Unfortunately, it doesn’t include info on which are patented.

We cover the new strawberry bed in newspapers and hay. Our method prior to using landscape fabric. Note the drip tape in position below the mulch.
Photo Luke Stovall

Climate change, challenges and options

Our climate is variable, and is changing to more of all extremes, so we need to change our systems to meet the challenges. It always helps to have a plan B.

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Fruit still available in May

If your rhubarb flowers, cut off the flower stems, preferably before the buds open, to keep the energy for the stalks.
Photo Pam Dawling

Rhubarb can be harvested until the stems get too thin. April is its main month here in central Virginia. Weed and water. Lop off any flower heads or buds, to concentrate energy into the stems.

Other fruit care in May

Install blueberry netting before the fruit sets, so the birds will have no reason to be interested. Weed, water, top up mulch, as needed. Check periodically to ensure the netting has no holes.

Grapes: Mow, weed, water in drought. Mow aisles as needed. New vines: remove side branches from trunks, and fruitlets. I like to walk through in May to record the condition of the grape vines.

A young grape vine in early May.
Photo Bridget Aleshire

Green Beans All Summer

A newly emerged bean bed with sunflower landmarks. When lilac is in full bloom, plant beans, squash, corn.
Photo Pam Dawling

Here I’m talking about snap beans, both bush beans and pole beans, often simply called green beans. By choosing appropriate varieties and giving thought to planting dates, you can get high yields all summer until frost.

Bean Varieties

We like Provider and Bush Blue Lake snap beans for productivity and flavor. We often sow Provider for the early and late crops, with Bush Blue Lake during the main season. Contender may have more flavor, but is less productive then Provider. Jade is a delicious, very tender bean, which grows well in hot weather, but will be a dismal failure if the soil is too cold. Our approach is to plant a succession of 6 sowings of bush beans, so we always have some at the peak of production.

Those who like flat beans often choose Romano II as a reliable producer of tasty beans whether it is hot or cool, wet or dry. Some people like yellow (wax) beans for visual diversity – the flavor is not much different from green beans. Purple-podded beans look attractive while raw, although the color fades on cooking.

Yellow wax beans.
Photo Small Farm Central

We have given up on pole beans as we don’t like putting up trellises. If the advantage of standing to harvest beats the disadvantage of putting up a trellis, you’ll prefer pole beans over bush varieties. Pole beans take a few days longer to mature but can then be picked for a longer period, if they don’t get damaged by the Mexican bean beetle. Half-runner beans can be grown with or without trellises, and are capable of high yields. We haven’t grown any we really liked.

Prepare for green beans

Beans tolerate a wide pH range, and like plenty of sun and well-drained soil. They definitely don’t thrive if flooded! An open site with good air drainage will help minimize mold problems and other leaf diseases. Bush beans take 50-62 days from sowing to first harvest, a bit less once the soil is really warm. A soil temperature of 77°F (25°C) is best for germination, although a temperature of 55-60°F (13-16°C) and rising is workable for dark-seeded varieties. Air temperatures of 65-85°F (18-29°C) are best for growth.

Like all legumes, beans produce nitrogen in their root nodules, although this doesn’t peak till after the beans are being harvested. In order to grow strong bean plants, you can fertilize before the beans at about 4 oz N/100 sq ft (13.4g/sq m), and use the bean-produced fertility for the following crop. If your soil is already very fertile, you could skip fertilizing before sowing the beans. Excess nitrogen will produce lots of leaves but delay flowering. 80-85% of the nitrogen produced ends up in the bean tops, so if possible turn them under before planting the next crop, rather then remove them to the compost pile.

Because they are not planted until spring is well underway, beds for beans can grow a good stand of winter cover crops ahead of the bean crop. Winter rye should be turned under three weeks ahead of sowing, to allow the rye to break down and for the allelopathic compounds to break down. We have found wheat to be easier to incorporate and to have less of an inhibiting effect on germination of the next crop. It is usual to avoid legume cover crops ahead of legume food crops, to reduce the likelihood of spreading pests or diseases. For the same reasons, it is better to grow beans where there have not been other legumes for 3 years. Sclerotinia white mold can be avoided by rotating with sweet corn or other grass crops, and avoiding nightshades, brassicas, lettuce, or other legumes. 

Newly emerged beans (in rather dry soil).
Photo Pam Dawling

Start beans as early as possible

We make our first sowing 10 days before the average last spring frost date, and cover the bed with rowcover. Dark-seeded varieties are more resistant to rot in cold soils, so use these at least for the first spring sowing. To speed germination, soak the seed overnight (up to 8 hours) in tepid water. If the sowing has to be postponed after the beans are soaked, rinse them twice a day and drain. Plant in 3 or 4 days. If you wait longer than that, the rootlets will be too long and fragile.

Sow your beans

If possible, ensure the soil has enough water before you sow, as watering after sowing can cause crusting and also chilling injury to the seed from the cold water. Avoid irrigation for two weeks after sowing to reduce the chance of the seed rotting. Sow 1” (2.5cm) deep, a little shallower in spring, a little deeper in hot weather. Place seeds 2-3” (5-7cm) apart. We use the wider spacing for new seed, and the closer planting for one-year-old seed. Two-year-old beans often have a germination rate of only 50%, and are not worthwhile. 

You can plant beans 2 rows to a bed, or on-the-flat in single rows with enough space to accommodate the pickers. The best spacing for optimum yield is 36 sq ins (232 sq cm) per plant. For example, 2” in-row x 18” between rows (5 x 46cm). Another advantage of close spacing is that the plants are more upright, with the beans higher in the leaves. This is less space than recommended for areas prone to fungal diseases.

Planting soaked inoculated beans through holes in plastic.
Photo Brittany Lewis

Beans host nitrogen-fixing bacteria in nodules on the roots, and if you are growing beans on land that has not grown legumes before, or it’s spring and you don’t want to rely on the existing bacteria waking up, add some powdered inoculant. You could add this at each sowing, as it is cheap and easy, especially if the beans have been soaked. Simply scatter some of the black powder on the beans as if you were adding pepper to your dinner, then stir the seed gently. Each bean needs only a few specks of the inoculant to get started. Contrary to any rural myths, the inoculant does not speed germination.

Care for your beans

Don’t cultivate or harvest while the leaves are wet, since anthracnose, bacterial blight and rust disease are more likely to spread under these conditions. Hoe or machine cultivate while the bean plants are still small, and once they grow taller and bush out, few weeds will cause trouble. We have tried sowing beans through biodegradable plastic mulch, poking holes with rods and popping the seeds in. This crop stayed very clean, and withstood a drought caused by a crew member mistakenly pulling the drip tape out too soon. Sowing took a long time, and anyone tempted to try this would be advised to make a jig that punches multiple holes at once. In that way, the saved cultivation time, lack of diseases, and extended life of the plants might balance out the extra sowing time.

Using the bean dibble to punch holes through the plastic mulch (the soil is holding down the edges of the mulch).
Photo Brittany Lewis
Beans growing on biodegradable plastic mulch.
Photo Nina Gentle

Irrigation is most needed during bloom, pod set and pod enlargement. Time the watering so that the leaves dry before nightfall. Beans need around 1” (2.5cm) of water until the end of May, then up to double that in summer.

Carry on sowing beans as late as sensible

To calculate your last worthwhile sowing date, subtract the number of days from sowing to harvest from your first frost date. Then count back a further two or three weeks, whatever would be a worthwhile length of harvest period for you. If you don’t have rowcover for when it turns chilly, count back another week or two in case frost is extra-early. Our first frost could be October 14, and counting back 60 days gets us to mid-August. We go with a last sowing in early August. We pay attention to weather forecasts, and when frost threatens, we cover with rowcover on the cold nights. Usually this lets us get several more pickings before any serious cold weather arrives. During the day, rowcover would stop pollination, but it does not stop beans that have already set from growing to full size.

Bad damage from Mexican bean beetles on these bean leaves. Beetles will also attack the pods after a while, making them inedible.
Photo Wren Vile

Plant beans often for continuous harvest

Before we discovered the Pedio wasps to kill the Mexican Bean Beetles, we needed a new patch of beans coming into production every 2 weeks. We made 7 plantings at 15 day intervals. We now plan for a new patch to harvest every 20 days, sowing 6 times rather than 7. As well as saving space and sowing time, we get more beans than previously. Some of the time we pick from two overlapping patches.

To calculate the best planting dates for your farm, you’ll need four pieces of information: first possible planting date in spring, last planting date that will provide a crop in time before fall frost, first harvest date from each sowing you’ve done, and the number days you want to be picking from the same plants. For us, space is tight, and we want to pick from the same plants for 3 weeks, after which the yield goes down, and it takes too long to “search” for the ripe beans.

We determined our earliest possible and latest worthwhile harvest start dates, and then divided the period in between into a whole number of intervals. In our case we went for 20 days. If we expect the first beans to start coming in on 6/16 and the last ones on 9/24, then the period in between is 100 days long. If we want fresh beans every 20 days, we’ll need a total of 5 intervals between plantings, which is 6 sowings.

A May sowing of Provider beans in late June.
Photo Pam Dawling

Our records tell us that for harvest dates of 6/16, 7/6, 7/26, 8/15, 9/4 and 9/24, we need to sow 4/20, 5/14, 6/4, 6/26, 7/19 and 8/7. In practice we use sowing dates of 4/16, 5/14, 6/7, 6/29, 7/19 and 8/3. Notice that beans mature faster in warmer weather, and to keep up with them, we need shorter planting intervals later in the summer. Our sowing intervals are 28, 24, 22, 20 and 15 days.

Harvest your beans

We pick beans three times a week, going for pencil-sized pods with pliable tips. In our climate, beans can size up in two days. It’s important to nip through the stem of the pod, and not leave the cap part on the plant, as this is the part which signals to the plant whether to continue cranking out beans or stop and focus on ripening seed. For the same reason, it is important to pick and discard any oversize pods.

Like many warm weather crops, beans are liable to chilling injury if over-refrigerated. If possible keep the temperature above 40°F (4.5°C), or you risk having the beans become slimy and pitted. At 40-45°F (4.5-7°C) and 95% humidity, beans can be stored for 7-10 days. Temperatures above 45°F (7°C) are likely to lead to yellowing and development of fiber.

A plentiful supply of beans!
Photo Kathryn Simmons

Watch out for trouble

Scout the fields once a week, and keep a weather-eye open while harvesting or cultivating, to spot small problems before they become large ones. See the Cornell University 2016 Organic Production and IPM Guide for Snap Beans for detailed organic disease and pest control information.

Lifecycle of the Mexican bean beetle.
Photo Purdue University

By far the worst pest of beans we ever deal with is the Mexican Bean Beetle, a yellow-bronze beetle with eight black spots. Adults overwinter in plant debris, so clean up well in the fall, and try not to have your first bean planting be near the site of your last one the previous year. Here, the MBB emerge on the first cloudy day in early June. We used to flame each bean planting when numbers and damage became intolerable, and move on to the next planting. A smarter move would have been to plant a small early trap crop of beans deliberately at or near the site of the late beans the previous year, and then flame the trap crop when there are larvae, but not yet any pupae.

Nowadays we buy the parasitic wasps Pediobius foveolatus, ordering them as soon as we see the fuzzy yellow MBB larvae, which is the stage the wasps attack. The package contains mummified MBB larvae, with the wasps on the point of hatching. Set the open container under the bean plants close to some MBB eggs and larvae. Sometimes I shake out a few mummies here and there along the row. Once hatched, the wasps are very mobile, and will likely take care of your neighbors’ MBB as well. The Pediobius do not overwinter in our climate, but we have found that good control for a few years reduces numbers so that we can sometimes take a year off from buying the parasites.

See Using Pediobius Foveolatus as a Biological Control for Mexican Bean Beetles on Organic Vegetable Farms by Kim Stoner. Suppliers come and go, apart from the Phillip Alampi Beneficial Insect Rearing Laboratory, who we have been buying from for many years. Two other suppliers are Bugsforgrowers.com and Arbico, Read the instructions here.

Other insects that can damage bean crops include bean leaf beetle, potato leafhopper, seedcorn maggot, European corn borer and tarnished plant bug. Mites and slugs can also cause trouble.

The main defenses against disease are to keep the leaves as dry as possible. Consider orienting the rows to take advantage of the prevailing winds, planting on raised beds, using wide row spacing or in-row plant spacing.

Fungal diseases tend to be furry. Botrytis Grey Mold and Sclerotinia white mold are the most common.

Bacterial diseases of beans cause sunken or water-soaked brown spots perhaps with paler margins, on leaves and pods. Virus diseases cause leaves that are typically mottled, blistered or curled.

Most likely, it will be you enjoying your beans and not pests and diseases!

Spring Lettuce Transition

Our first outdoor lettuce bed in May.
Photo Wren Vile

We grow lettuce to harvest year round, here in central Virginia. From the end of April into November, we harvest lettuce heads outdoors, from our raised bed area. From October to early March we harvest outer leaves from leaf lettuces and romaines in our solar greenhouse, and in our solar-heated double-layer hoophouse from October to April. From mid-November we harvest salad mixes containing lettuce from our hoophouse. From 4 December to late May we have baby lettuce mix from the hoophouse. Note that we have overlaps at both spring and fall transitions. We’re approaching the spring transition, and that is what I am going to focus on in this post.

 Our Winter Hardiness Zone in central Virginia is 7a, which means our annual minimum temperature averages 0°F to 5°F (-18°C to -15°C).  Our average date of the last spring frost over the past 14 years is April 29 (later than 5/13 one year in 10).

Flats of lettuce transplants in our cold frame in April.
Photo Pam Dawling

More About Growing Lettuce

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

I have lots of posts about growing lettuce! Here are some of them:

Early Lettuce Production See this post for details of growing lettuce transplants in flats in our greenhouse.

Cold Tolerant Lettuce – In the 2017-2018 winter we had some extremely cold weather, with outdoor night-time temperatures of -3°F (-19°C) two nights, followed by -8°F (-22°C) 6 and -9°F (-23°C). Our guideline is that if we expect the night-time low to be 8°F (-13°C) or lower outdoors, we use rowcover in the hoophouse. It wasn’t enough to save all the lettuce. See this post for which varieties survived.

Ezrilla, a favourite cold-hardy lettuce.
Photo Wren Vile

Also see What makes vegetable crops bolt and how can I stop it?

And I have a whole year of Lettuce for the Month posts. See here for the overview. These posts are mainly about our favorite varieties for each time of year.

Head Lettuce Transplanted Outdoors

From February to November/December, we grow lettuce outside from transplants. Transplanting gets a head start on weed control, which is important all the way from planting out to a couple of weeks before harvest. Don’t waste time hoeing lettuce you will be harvesting next week. I generally find that if we hoe once, a couple of weeks after transplanting, that is all the weed control we need at the fast-growing time of year.

From mid-January until mid-March we sow in flats in the greenhouse, with heating for the January-March sowings, to get the seeds germinated, then good old solar energy to grow them to transplanting size. We spot the seedlings out to give the plants more space, and harden off the flats of transplants in our cold frame for two weeks before planting them in the garden. The first few plantings will get rowcover after transplanting, to protect the young plants from cold and speed up the growth rate. March 9 is our goal for transplanting our first sowing (January 17) outdoors. January 17 to March 9 is 52 days, a very long time for the seedlings to grow to transplant size! We hope to harvest that first lettuce as heads in late April.

During April we put the seed flats in the greenhouse without extra heating, as temperatures in the greenhouse are warm enough to germinate the seeds. Growth speeds up, and in warm weather we transplant three weeks after sowing. The intervals between one transplanting date and the next decrease from 9 days in spring to 5 or 6 days in summer. We transplant 120 lettuce from each sowing – about one week’s worth for 100 people.

Swordleaf lettuce, and an unnamed romaine with radishes. Photo Bridget Aleshire

Soil Temperatures for Lettuce Germination

The soil temperature range for germination of lettuce seeds is 35-85°F (2-29°C), with 40-80°F (4-27°C) being the optimum range and 75°F (24°C) the ideal. At 41°F (5°C) lettuce takes 15 days to germinate; at 50°F (10°C) it takes 7 days; at 59°F (15°C) 4 days; at 68°F (20°C) only 2.5 days; at 77°F (25°C) 2.2 days. Then the time to germination increases: 2.6 days at 86°F (30°C); after that it’s too hot. A soil thermometer soon pays for itself and saves lost crops and frustration.

Summer Lettuce Nursery Seedbed with Concept, De Morges Braun, New Red Fire and Loma lettuces.
Photo Bridget Aleshire,

Bare-Root Transplanted Lettuce in Summer

From May to late September we use an outdoor nursery seedbed and do bare-root transplants (with heat-tolerant varieties). The soil temperature does not vary as much as the air temperature, and  we no longer worry about cool nights.

If it’s too hot for lettuce seed to germinate, you can find a cooler place (put a seeded flat in a plastic bag in the fridge or on the concrete floor in the basement). Or cool down a small part of the world. From June we put shade-cloth over the lettuce seedbed, and only sow in the evening. In July and August, we water the sowed seedbed with freshly drawn cold water, line up ice cubes along the seed rows, and cover with shade cloth.We make sure to keep the seedbed damp, using cold water each time.

See Using ice to germinate lettuce seed in hot weather

From July to September we sow lettuce every 5 days! See Success with summer lettuce. Of course, transplanting that lettuce in hot weather takes care too. We do that late in the day, and water as we go. We cover the transplants with hoops and shade-cloth, and water daily until they are well established. We stop sowing for outdoors on August 29.

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

Lettuce After Summer Ends

From September 11-17 we sow lettuce in a nursery seedbed to transplant in our greenhouse, and on September 15 and 24 to transplant in our hoophouse. This is our fall transition and I’ll write about that when the time comes.

Workhorse Crops for April

 

Garlic beds in April. Cabbage under rowcover on the left, strawberry beds on the right. Photo Kathryn Simmons

This is the last month in my series of 14 Workhorse Crops (asparagus, beans, cabbage, carrots, chard, collards/kale, garlic, potatoes, sweet corn, sweet potatoes, tomatoes, watermelons, winter squash, zucchini/summer squash). These crops are reliable and productive under a range of weather conditions.

Here are links to the other 11 months:

Spring is here. April is a busy month for sowing and transplanting! First the rest of the cool weather crops, then the first of the warm weather crops. Our average last frost (over the past 14 years) here in central Virginia is April 29. We reached 12 hours of daylight on the March 20 Equinox, and the days lengthen until the summer solstice.

Gentry yellow squash newly transplanted into our hoophouse, with a friendly wood sorrel!
Photo Pam Dawling

In our hoophouse we are transplanting squash, cucumbers, and peppers in April. Those crops will occupy the centers of the beds, before taking over the whole width. By that time, we will have harvested any remaining winter salad crops, and the spinach we transplanted in early March. Our greenhouse and coldframe are packed with transplants.

Workhorse Crops to Plant in April

Newly emerged beans (in rather dry soil).
Photo Pam Dawling

Beans

We sow our first green beans April 24, around our last frost date. We choose two reliable varieties, Provider and Bush Blue Lake. Or Contender. There are varieties that are more delectable and tender, like Jade, but those are less cold-tolerant, and so not good for the first planting. We soak the bean seed overnight before planting.

We sow 2 rows in a 4ft (1.2 m) wide bed, with the rows about 16” (40 cm) apart. Seeds about 3” (7 cm) apart, closer if they are leftover from last year. Bean seed does not germinate well if older than that.

We use inoculant to help the nitrogen-fixing bacteria get started. We probably have plenty in the soil by now, but early in the year, everyone is a bit slower to get moving!  We cover the beds with rowcover until the weather has settled warm.

We make 6 sowings of beans. Our sowing dates are 4/24, 5/8, 5/24, 6/8, 6/24 and 7/8. The intervals between plantings are 14, 16, 15, 16 and 14 days. This schedule has got a bit off-course and has a much earlier end date than necessary. A better set of dates would be 4/20, 5/11, 6/1, 6/22, 7/13 and 8/3, at intervals of 21 days. The rate of maturity of beans does not vary much with temperature.

Cabbage

We are not growing any storage cabbage this spring, due to those infamous staff shortages everyone is struggling with. If we had sown some in early February, we would be transplanting them April 1, and covering the bed with ProtekNet for as long as possible to keep the bugs off. If we used rowcover when we first transplanted them, we remove it in April to use elsewhere (broccoli). Cabbage to store for the summer can be a great way to have greens other than chard during hot weather.

A tidy bed of young carrots. Photo Kathryn Simmons

Carrots

From April we switch to sowing one bed per month until August. We sow our fifth carrots April 10, and our sixth in May. The April sowing takes about 11 days to germinate, depending in on the soil temperature. Our standard practice is to flame weed carrots before the seedlings emerge. In April we have lots of weeding and thinning of carrots sown earlier.

Chard

We sow chard (and leaf beet, the type of chard closest to spinach) on March 24, and transplant on April 22, with two rows in a bed, close together down the middle, to leave the paths free for us. Chard will be our main summer leafy green after the brassicas have all bolted. We usually do a mix of a multicolor type for beauty, Fordhook Giant for reliability and productivity, and Perennial Spinach leaf beet as insurance. The leaves are smaller, making it slower to pick, but it does taste more like spinach than any of the other chards, and it is very resilient.

Young sweet corn plants.;
Photo Bridget Aleshire

Sweet Corn

We sow our first sweet corn on April 26, being sure to choose varieties such ads Bodacious, with good cold-soil emergence. We also sow some Speedling flats on the same day, and float them in a n outdoor tank, as a care-free way of having some backups to transplant as replacements for casualties if a late frost strikes. Our harvest goal with our fist sowing is July 4-18. Our 6 sowings of sweet corn are scheduled to give us an even continuous supply, with a new planting coming on-stream every 15 days. We harvest three times a week

Potatoes

Potatoes can be planted here in April, but we prefer to divide our planting in two, half in march, half in June. Click the link for more about every stage of potato growing .

A row of squash plants with ProtekNet to keep bugs off until flowering.
Photo Pam Dawling

Summer Squash/Zucchini

We transplant our first outdoor summer squash and zucchini (as well as the ones we grow earlier in the hoophouse). We start them in the greenhouse March 27, in 6×12 Speedling flats. Those cells are bigger than the Winstrip 50 cells. We like Tender Gray 42d zucchini, a light-colored Middle Eastern variety, and Zephyr 54d yellow squash with distinctive green tips. We transplant them 4/21 with rowcover or ProtekNet to keep the striped cucumber beetles away. Other squash pests (Squash bugs, Squash Borers) are not such a problem for us. From the second sowing onwards, we direct sow outdoors, as the soil has warmed up by then. We often transplant or sow nasturtiums in among the squash (or the cucumbers) to deter cucumber beetles. We also enjoy the flowers.

Greenhouse sowings for later transplanting outside, and other greenhouse work

In April in the greenhouse, we sow our watermelons, and paste tomatoes if we’re growing those, and some non-workhorse crops, of course.

Watermelon transplants in a Winstrip plug flat. Watermelons give earlier harvests from transplants, and plants in plug flats transplant easier then from open flats.
Photo Pam Dawling

Watermelon

Watermelons need warm soil. We’re not growing any this year. Our method has been to sow them in Winstrip 50-cell trays in the greenhouse April 26, and transplant them into biodegradable plastic mulch (with drop tape under it) May 11. (We use 3’ (1 m) spacing with rows 66” (1.7 m) apart. We rowcover the transplants for 3 weeks, until flowering, and then remove the covers to allow pollination to happen.)

Winter Squash.

Winter squash is normally such a lovely, easy crop! Direct sow, water, thin, hoe, till between the rows until the vines run, then ignore them (apart from watering) until September. We have mostly grown Moschata types as they have the best resistance to squash bugs, and they store really well. Our favorites include Waltham butternut, Cha-cha Kabocha, Cheese Pumpkins, Jarrahdale squash and the giant Tahitian Butternut. We direct sow May 26, but if there are particular challenges with constant rain preventing us preparing the soil, we have transplanted, from cells sown in late April.

Potting Up

Pepper transplants in our greenhouse. Photo Kathryn Simmons

We pot up the peppers and eggplant for transplanting outdoors in May. Eggplant needs to be kept above 55°F (13°C), peppers above 50°F (10°C) and tomatoes above 45°F (7°C).

Sweet Potato Slips

Also, we continue cutting sweet potato slips. I covered growing sweet potato slips last week.

Workhorse Crops to Plant in the Hoophouse in April: Squash, Cucumbers, Peppers

North edge bed in our hoophouse flagged up for digging holes to plant peppers.
Photo Pam Dawling

We plant one bed each of these crops, measuring and digging holes 2’ (60 cm) apart down the center of the bed, and adding a shovelful of compost to each hole. We do not clear the winter crops from the beds before transplanting the new crops. We value the extra month of greens we can harvest this way. When the new crops are small, they don’t need the whole space, and I’ve even thought that the slight shade from the greens helps the new transplants settle in.

We grow a bush (non-vining) cucumber Spacemaster, and two early squashes, sometimes Golden Glory zucchini and Zephyr. The bell peppers are Lady Bell, Gilboa (orange) and Revolution, all fairly early, big, thick-fleshed  and tasty.

Hoophouse Tomatoes

In April we install the posts for tomatoes (hopefully we won’t need to use rowcover at nights any more, and start string-weaving. We use the Florida string-weaving (or basket-weaving) technique to support our plants. More about that task in future.

Workhorse Crops to Harvest in April

Asparagus

Asparagus photo Kathryn Simmons

The asparagus harvest season usually begins for us in early April. Well prior to that date we root out early weeds.  Then we fertilize with fish meal and greensand or a complete fertilizer, or add a thick layer of rich compost (if we did not do this in the fall), spread over the whole bed.  Next, mulch to a depth of at least 4” (10 cm) for weed control, with wood chips, wood chip horse bedding, sawdust, straw or old hay (although hay may include weed seeds).

I recommend snapping asparagus spears at ground level – cutting them below the soil surface risks damaging emerging spears. Harvest in the early morning, as the spears are easier to snap before they warm up. Snapped asparagus is almost all tender and usable – the tough lower ends remain in the soil. If you expect a frosty night, harvest all spears, regardless of size, as they will otherwise freeze and be wasted. We have sometimes done a second (afternoon) harvest, if we’ve noticed a cold forecast. During the harvest season, ensure the asparagus gets 2” (5 cm) water each week.

At the beginning of the season, when the weather is cooler, spears can grow to 9-10” (22-25 cm) before ferning out, but in warmer weather, they will open out at a shorter height.  So, expect to harvest shorter spears in warmer weather. To keep life simple, we tell our crew to pick any spears 7” (17 cm) or taller. You may prefer to change the required length according to the temperature. Harvest anything of the right length, regardless of thickness. For pest management, we pick and later discard skinny, tough spears, and any that are ferning out. (Slender stems are not more tender than large ones, quite the contrary.) We harvest the entire patch every single day as a way of controlling asparagus beetles – no spears are left long enough to leaf out, and beetle eggs are removed (on the spears) and cannot hatch. The eggs are harmless, and can be washed off after harvest by spraying with water, or tub-washing.

We harvest into short buckets so that the spears will be standing on end when the bucket is upright. We add a small amount of water, to keep the spears fresh, and hurry the buckets to a cooler at 34-40°F (1-5°C).

Asparagus photo by Kathryn Simmons

First year after the planting year

Trials now show that asparagus yields more long-term if it is lightly harvested for 2-4 weeks in the first year after the planting year, in contrast to previous directions to wait 3 or 4 years. Stop harvesting after 4 weeks at the most, as soon as the thickness of most of the spears is less than the size of a pencil.

After the first (short) harvest season, let the spears grow tall and fern out. The photosynthesis of the ferns feeds the crowns and strengthens them for next year’s growth. Established asparagus is fairly drought-tolerant, but immature plantings need 1” (2.5 cm) of water each week. By the fall ferns will be 4-5’ (1.2-1.5 m) tall. Apply compost every year in the fall or winter.

Second year culture

In late February or March, we weed, spread compost (if we didn’t do it in the fall) and mulch to a depth of at least 3” (7.5 cm). We harvest for perhaps 5 or 6 weeks in the second year after the planting year. Stop picking when the thickness of most stems is less than a pencil. By the end of this second season the asparagus ferns will likely reach a height 6-8’ (1.8-2.4 m).

Third year and future years

Weed, spread compost, mulch, harvest and irrigate, weed, mulch. Pick asparagus for perhaps 6 weeks in the third production year, stopping when the spears are thin. By the fifth year you should reach a maximum harvest season of 8-9 weeks.

Chard – our hoophouse chard is growing at a good rate. This winter we started late, and so we have only been able to harvest the chard small, for salad mixes. In April we will get leaves large enough to cook.

Bright Lights chard.
Photo Pam Dawling

Collards and Kale can be harvested all month (over-wintered plants) until they start bolting. The spring-planted ones outdoors are ready from mid-April.

Overwintered Carrots and Cabbage are a possibility some years, but not this one!

Garlic scallions are still available to harvest here. We dig the plants once the leaves have reached at least 7” (18 cm). Wash and trim, cook and enjoy! Some years we have made a big planting, and it has provided for us into May (when they will start to bulb).

Hoophouse Workhorse Harvests in April

Our Red and White Russian kales are now producing well. These are Siberian-type kales, that keep growing (a bit!) in cold weather. We harvest the outer leaves and stand them on end in a bucket in a little water. The wilt very easily, so we try to keep them in the shade and get them to the cooler promptly.

Workhorse Crops from Storage in April

In April we can eat cabbage carrots, garlic, potatoes, sweet potatoes, and winter squash from storage, while they last. We do still have potatoes, sweet potatoes and butternut squash. Also we have frozen summer goodies, and pickled things, sauerkraut, pickled beans, and canned goods like salsa.

Workhorse Crops Special Topic for April: Rowcover

A rowcovered bed of turnips.
Photo Bridget Aleshire

Use rowcover to keep new transplants outdoors protected from cold until they are acclimated and /or the weather warms up. In the hoophouse in April we use rowcover on possible frosty nights, to protect our new tender crops.

Rowcover is lightweight, easy to use, and easy to store. Its biggest challenge is that you need to hold down the edges with bags of rocks or sand, plastic jugs of water, or metal or wooden stakes rolled in the edges, to stop it blowing open or even blowing away!

To protect against cold, you need thick rowcover. We think polypropylene rowcover lasts longer and is tougher than polyester (Reemay). We like Dupont Xavan 5131 (aka Typar). 1.25 oz/sq yd spunbonded polypropylene, with 75% light transmission, and about 6 F (3.3 C) degrees of frost protection. It can last for 6 years or more.

Thinner types are made to protect from insects – if you already have thin rowcover You can double it up for cold weather use. Thinner types are very fragile and are easily torn by inexperienced helpers.

Double hoop system for winter rowcover.
Pam Dawling

Hoops keep rowcover from sticking to frozen leaves and reduce abrasion. For winter we made double wire hoops. 9- or 10-gauge wire inner hoops, 22 gauge outer hoops, every 6ft (2 m) down the length of the row.

See Workhorse Crops for March for info on Predicting Frost

Blueberries.
Photo Marilyn Rayne Squier

For my next series of crops for the month, I’m planning to write about small fruits (berries and melons)

Three Methods of Growing Sweet Potato Slips

Growing sweet potato slips in an old fridge used as a warm insulated cabinet.
Photo Kathryn Simmons

Sweet potatoes are grown from “slips,” (pieces of stem with a few leaves), grown from a mother root, not from seeds or replanted roots. We used to buy bare-root slips for transplanting, because we didn’t know how to grow our own, and had heard it wasn’t easy. We have been growing our own for many years now, and prefer the flexibility and reliability it gives us. We did make several mistakes initially, so I can warn you about what not to do. We have a system that we really like, and I have learned a few other methods that I will also tell you about, including one I helped out with the past two years, growing them in a hoophouse.

Disadvantages of buying sweet potato slips

  1. You need to specify a shipping date months ahead, then hope for good weather and no shipping delays.
  2. You might have late frosts, spring droughts, or El Niño wet springs, and climate change is only adding to the uncertainty, but slips that arrive in the mail need immediate attention.
  3. You have to get them all in the ground promptly, and do your best to keep them alive (because they arrive wilting).
  4. Some amount of drooping (transplant shock) is normal.
Cut sweet potato slips in water.
Photo Kathryn Simmons

Advantages of growing your own sweet potato slips

  1. You can delay planting if the weather is all wrong (frost, drenching rain, heatwave)
  2. You can grow them big and plant 3-5 nodes underground, giving more chance of survival if there is a late frost, or an early drought.
  3. You can plant them in stages rather than all on one day.
  4. You can grow extra and keep them on hand to replace casualties.
  5. The sturdy plants get off to a strong start – the transplants don’t wilt – a big advantage where the warm season is on the short side for a 90- to 120-day plant.
  6. You have more self-reliance and less money going out.

 How not to grow sweet potato slips

I made several mistakes learning to grow slips. You don’t have to repeat my mistakes! My first error – following directions written for much further south (in pre-internet days), was to try growing slips in mid-January in central Virginia. Dismal fight against nature! Likewise, I was puzzled by talk of using cold frames. Ours were freezing cold at that time of year.

Next, I set up a soil warming cable in a cinder-block-enclosed bed on the concrete floor of our greenhouse. This is how I discovered most soil warming cables have thermostats that switch off the heat at 70°F (21°C). I just couldn’t get the soil warm enough.

Sweet potatoes on a plate.
Photo Brittany Lewis

Three Successful Methods of Growing Sweet Potato Slips

  1. Twin Oaks slips-in-flats method
  2. Boutard single node cutting method
  3. Hoophouse or caterpillar tunnel bedding method (Twin Oaks)
Flat of home-grown sweet potato slips.
Credit Kathryn Simmons
  1. Twin Oaks Slips-in-Flats Method

I’ve written about this before, so I’ll just give you a link to open another page.

Starting Sweet Potato Slips discusses pros and cons of growing your own slips, and describes our “slips in flats” method, which I learned from Hiu Newcomb of Potomac Vegetable Farms. Here is our Worksheet we use to stay on track with that task.

Sweet Potato Plan 2022

 

Single-node sweet potato slip at 16 days.
Photo Anthony Boutard
  1. The Boutard single node cutting method

Anthony Boutard and Caroline Boutard Hunt wrote an article about single node sweet potato propagation (which they learned from John Hart of Cornell) in Growing for Market in March 2015. They farm in Oregon and New York respectively.

Both the slips-in-flats method and this one start at the same time, planting roots in damp compost in a warm greenhouse. I corresponded with Anthony Boutard about our respective methods. He pointed out that the slips-in-flats method needs a lot of warm space to grow the slips, at a time when warm space is at a premium. Our method does take us from early March to mid-May.

The single node cutting method uses only 10-20% of the number of mother roots compared to the slips-in-flats method. It uses tiny plants in plug flats, saving on greenhouse space, and only needs 18 days between cutting the slips and planting in the field. The smaller plants can experience less transplanting shock than larger plants. On the other hand, I do not think they have the resilience that multi-node plants have, for example if a late frost strikes.

When these plants grow in the field, their root production is from the single node. This can lead to fewer, but very large tubers, an advantage or a disadvantage, depending on your goals. Better in climates with a short warm season than in hot places, although digging after a shorter growing period would be possible in warm climates.

This method can be used to grow more plants from purchased cut slips, which is very helpful if you are growing a rare heirloom with limited propagation material available. Plant the bought slips in the greenhouse and grow them on until you can make cuttings.

Like the slips-in-flats method, this one buys time if the weather turns bad and you need to back pedal on your planting out date.

Single-node sweet potato slip showing roots three days after striking the cutting.
Photo Anthony Boutard.

To prepare single node cuttings, cut a slip from the mother tuber and cut off about ¼” (6mm)  above a leaf node (the swollen point where the leaf emerges). In the leaf axil is a bud which will grow a shoot, and just below the bud is a ring of cells that can grow roots. You can trim back the leaf stem, or leave the leaf on. Make the second, lower, cut just above the next node down. You can make several cuttings from one regular slip.

50-cell plug flats work well to grow the cuttings. Push the lower end of the shoot cutting at an angle into the cell, creating an even V with the leaf stem. If a cutting is too tall to fit your cell plugs, you can cut more off the lower end. The new shoot will then grow upwards easily from the bud in the leaf axil.

Keep the trays warm and moist, and plant out after only 18 days, into well-prepared damp soil, with drip tape in place. Delaying planting for 10 days or so is not a problem.

This post includes a discussion of the Single Node Method, in an article in Growing for Market magazine by Andrew Schwerin from NW Arkansas. In warm climates, only use this method if you want really big tubers!

Hoophouse beds of sweet potato mother roots in early May
Photo Pam Dawling
  1. The Hoophouse Bedding Method

I learned this method from my friend and colleague River Oneida, who grew slips for Southern Exposure Seed Exchange. He planted up 4 beds 45’ (14 m) long with three rows/bed in a single-layer hoophouse and grew an average of 4000 slips/week, for a 6 week sales season (24,000 slips), with a peak and bell-curve ends of the season. Caterpillar tunnels could also work.

Store your saved roots at room temperature. From March 1 onward: start the sweet potatoes sprouting indoors in stages, as heated space permits, at 85°F (29°C), and high humidity. Remove any rotting potatoes. When each potato grows ¼” (6 mm) sprouts, take it out of the heated space and replace with new ones. Put the ¼” (6 mm) sprouted ones at room temperature to slow them down for batching with later ones.

In March:  Cover the bed area in the hoophouse with a single layer of clear plastic, and kill any weeds that pop up. Four weeks before shipping starts (on April 1 in central Virginia), prepare the beds in the hoophouse. Dig out a flat-bottomed bed 1” (2.5 cm) deep, and set the sprouted sweet potatoes an inch (2.5 cm) apart in rows. One or two sprouts are enough. If possible, don’t bed unsprouted roots

Spread some compost, not lots. Replace the soil you dug out, on top of the sweet potatoes. Add soil from the aisles, putting 1”-3” (2.5-7.5 cm) of soil on top of the potatoes. Not more. Set out drip tape and irrigate regularly.

After bedding, stab holes in the plastic every 4” (10 cm) for respiration. Check regularly, opening the plastic on warm days once slips are visible. In mid-April or whenever you see slips emerging, remove the plastic in the daytime, but put it back for frosty nights Add more soil later to cover exposed tubers if needed. Regulate temperature if you want a faster or slower rate of production.

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

Some slips will be ready from the 3rd or 4th week of April onwards. If too many slips are ready at any point, pull and heel them in outdoors. Remember to water.

I first wrote this up for an article for Growing for Market magazine, and have included it in my updated slideshow, at the end of this post. It’s a great method for people growing lots of slips (for instance, for sale). It could also be used for smaller amounts, by occupying a corner of a hoophouse growing other crops at the same time.

More Posts on Sweet Potatoes

I have written a lot on sweet potatoes at all stages from propagating our own slips, growing them all summer, and harvesting. My posts include:

Sweet Potato Propagation and Yields

Transplanting Sweet Potatoes (biodegradable plastic; deterring deer)

Planting Sweet Potatoes, includes stages of growth, and links to many other sweet potato posts, including most listed here.

Growing High Yielding Sweet Potatoes

 Sweet potato harvests over the years (2020) summarizes my writing about harvesting, including Harvesting Sweet Potatoes (2016); Sweet Potato Harvest (2015) and again (2015) and earlier (2014) and in 2013, 2012

What Makes Sweet Potatoes Sprout (during storage)

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

More information

For more info, see

ATTRA Sweet Potato: Organic production

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

I have an updated Sweet Potato Slideshow  

Growing Sweet Potatoes from Start to Finish 2021

Workhorse Crops for March

 

Flats of transplants in our cold frame ready for transplanting.
Pam Dawling

We’ve just got a few months left in my monthly series of 14 Workhorse Crops (asparagus, beans, cabbage, carrots, chard, collards/kale, garlic, potatoes, sweet corn, sweet potatoes, tomatoes, watermelons, winter squash, zucchini/summer squash). These crops are reliable and productive under a range of weather conditions. You can use the search box to find other posts in the series, such as February.

Spring is on the way! Many more crops to plant this month! Our average last frost (over the past 14 years) here in central Virginia is April 29. We reach 11 hours of daylight on February 20, and we and everyone else will reach 12 hours on the March 20 Equinox. It’s all go!

In our hoophouse we are clearing bolting crops and transplanting spinach (the “Racehorse” of this series) wherever we have space along the edges of the beds. The tomatoes go in in March and squash, cucumbers, and peppers in April. Those crops will occupy the centers of the beds, before taking over the whole width. Our greenhouse is filling up with transplants.

Workhorse Crops to Plant in March

Young spring cabbage with a hay mulch. Wren VIle
Cabbage

We transplant our early cabbage around March 6. We had trouble with mice in the greenhouse in early February and lost quite a few seedlings. We also made the mistake of using seed that was too old. So we will have only one bed of early cabbage this year, not two. We did try to make up for the losses by resowing fast-maturing varieties, but we still ended up short. We like Farao (60d) and Early Jersey Wakefield (63d). Both numbers are seed to harvest. Subtract 20 days if counting from transplanting to maturity. We will cover the bed with thick rowcover for the first few weeks after transplanting.

Carrots
Newly emerged carrots with indicator beets.
Photo Kathryn Simmons

We sow carrots in mid-March, and again at the end of March. The mid-March sowing takes from 9-19 days to germinate, depending in on the soil temperature. The end of March sowing takes 9-12 days. We sow a few Indicator Beets at the beginning of the bed. Beets germinate one day sooner than carrots at almost any temperature. When we see the red loops of the beet stems emerging, we know it’s the day to flame weed the carrots.

Chard

We sow chard (and leaf beet, the type of chard closest to spinach) on March 24, but you can start earlier if you want earlier harvests. Chard seed will germinate from 41°F (5°C) to 95°F (35°C), and the best temperature is 86°F (30°C), when it needs only 4 days. Our goal is to use chard as our main summer leafy green after the kale, collards, broccoli and Asian greens have all bolted. In spring we usually have lots of cabbage, broccoli, collards and kale. Maybe we should do some earlier chard this year to make up for lack of broccoli and troubles with cabbage and over wintered kale?

Collards and kale
Young collard plant (Morris Heading, I think) Pam Dawling

In mid-March we will be transplanting Vates kale and Champion or Georgia Green collards directly from the soil in our hoophouse out into the garden. We usually grow Morris Heading collards but this year we are trying something different. We’ll use rowcover for the first few weeks. I have written before about bare-root transplants. This method saves us a lot of time, and saves greenhouse space. See Workhorse Crops in February for details about sowing these crops in the hoophouse.

Potatoes

Another mid-March task for us is potato planting. I wrote a whole series about every stage of potato growing last year. So I won’t say more here.

Hoophouse beans
Tomatoes, green beans and cucumbers in June.
Photo Alexis Yamashita

We don’t grow green bush beans in our hoophouse every year, but this year we will. As with other late winter/early spring hoophouse crops, we sow beans in our hoophouse a month earlier than we can sow outside. We aim to sow in the hoophouse on March 20. Of course, if it is particularly cold then, we will wait. We’ve found that beans sprawl more in our hoophouse, so we buy an upright fast-maturing variety, such as Strike.  We’ve also found that the edge beds are too cold for beans in late March, so if the crop rotation would have us use an edge bed, we sow beets or some other crop instead. We will use thick rowcover on nights that are forecast to be frosty outdoors. See mention of hoophouse beans in January.

Hoophouse tomatoes
March hoophouse bed prepared for tomato transplants – holes dug, compost added.
Photo Wren Vile

Mid-March is our target transplanting time for tomatoes in the hoophouse. We grow two beds, one of earlies (less than 71 days) and one bed of reliable favorites (Tropic, Jubilee) along with two plants each of other varieties we like or are trying out. Each 96ft (29 m) bed has two cherry or grape tomato varieties, with two plants of each. We plant the shortest varieties at the east end and the tallest (the cherries) at the west end, so that all the plants get the best possible light. (Our hoophouse has the long walls on the south and north.) We update our Tomato Rampancy Rating list each year.

This year in the early bed, we are growing Five Star Grape 62d, Sun Gold 57d, Garden Peach 71d, Mountain Magic 66d, Stupice 62d and Glacier 56d. Mountain Magic is a new favorite (it doesn’t suffer from green/yellow shoulders) and we have increased the number of those plants, reducing numbers of Stupice and Glacier.

Hoophouse tomatoes with yellow shoulders. Glacier or Stupice.
Photo Pam Dawling

In the other bed we are growing Cherry Bomb 64d, Black Cherry 64-75d, Geronimo78d, Striped German 78d, Amy’s Sugar Gem 75d, Green Zebra 72-86d, Cherokee Purple 72-85d, Tropic 80d, Jubilee 80d, Estiva 70d, Pink Boar 75d, and Mountain Fresh Plus 75d.

We use the Florida string-weaving (or basket-weaving) technique to support our plants. More about that task in future.

Indoor sowings for later transplanting outside or in the hoophouse

In March we will sow our hoophouse cucumbers and squash, and our outdoor peppers, eggplant, maincrop tomatoes, and our first outdoor zucchini and summer squash. And some non-workhorse crops. Also, we start our sweet potato slips. I covered growing sweet potato slips in another post. On March 24 we start our chard, as already mentioned.

Workhorse Crops to Harvest in March

Collards and Kale can be harvested outdoors here in March, from overwintered plants. This past fall, we were late getting our kale established and the combination of a mild December and a cold January has damaged them badly. We had 3 nights in January down to 10°F (-12°C). Normally we can harvest those beds once a week each in March. Our mnemonic for sustainable harvesting of leafy greens is “8 for later”, meaning we leave at least eight inner leaves when harvesting the outer ones, to ensure the plants have enough strength to regrow.

Overwintered Carrots and Cabbage are a possibility some years, but not this one!

Garlic scallions prepared for sale. Typepad.com

Garlic scallions are ready to harvest here from mid-March. These baby garlic plants offer a welcome change form leafy greens and root vegetables. We start to dig the plants once the leaves have reached 7” (18 cm). Wash and trim, cook and enjoy! Yes, you can eat them raw if you like! Some years we have made a big planting, and it has provided for us into May (when they are starting to bulb).

Hoophouse Workhorse Harvests in March

Our Red and White Russian kales are now producing well. These are Siberian-type kales, that keep growing (a bit!) in cold weather. We harvest the outer leaves and stand them on end in a bucket in a little water. The wilt very easily, so we try to keep them in the shade and get them to the cooler promptly.

White Russian kale ready for harvest in our hoophouse. Photo Pam Dawling

Bulls blood beet greens, chard, and some greens not in our Workhorse group, (turnip greens, and spinach) are still going strong. Our experimental carrots are still doing OK, although I’m not a fan of giving them hoophouse space for such a long time with no harvests. I think we would have done better to harvest them in December. The foliage is getting bedraggled, and I fear the roots are getting woody and less sweet. This is all an experiment by one of the others on the crew, who will be studying the results.

Workhorse Crops from Storage in March

In March we can eat carrots, garlic, potatoes, sweet potatoes, winter squash and cabbage from storage, while they last. We do still have potatoes, sweet potatoes and butternut squash. Also we have frozen summer goodies, and pickled things, sauerkraut, pickled beans, and canned goods like salsa.

Garlic beds next to rowcovered broccoli beds, under a stormy sky.
Photo Wren Vile

Workhorse Crops Special Topics for March: DIY Weather Forecasting

Learn your local weather patterns by keeping records of daily max and min temperatures and rainfall, and watching what happens.

Our mid-Atlantic climate is controlled by three weather systems, mainly by moisture from the Gulf of Mexico, the Bermuda High Pressure area in summer, and recurrent waves of cold Canadian air in winter.

Rain (statistically fairly evenly distributed throughout the year in our county) has slight peaks in January, February and March and again in early June and August.

Some parts of our area can experience long periods of drought: September-November is the drier season but it’s also the hurricane season, so the net result is very variable.

We use Wunderground forecasts, but subtract 5F° (2.5C°) from their forecast night lows for our nearest town, and mentally downgrade the chance of rain by 10%, as rain often passes us by as it scoots along the river valley north of us. 3/30 pm in winter is a good time to look at the night forecast.

WeatherSpark is a great resource. You can enter your zipcode or town and discover a large range of charts and graphs about weather in your area. It will help you learn what to expect.

Immature frosty cabbage. Photo Lori Katz

As for predicting frost, here are some of the factors to consider, that make frost more likely here:

  • If the date is after 10/14 or before 4/30 (ie within the average range for frosts here)
  • If the Wunderground forecast low for Louisa Northside is 37°F (3°C) or less.
  • If the daytime high temperature was less than 70°F (21°C).
  • If the temperature at sunset is less than 50°F (10°C).
  • If the sky is clear.
  • If the soil is dry and cool.
  • If the moon is full or new.
  • If there is little or no breeze, although if temperatures are falling fast, the wind is from NW and the sky is clear, then polar air may be moving in, and we’ll get a hard freeze.
  • If the dew point forecast is low, close to freezing, a frost is more likely. Frost is unlikely if the dew point is 43°F (6°C) or more.

Growing flowers to attract aphid predators in early spring

Borage flowering in our hoophouse in January, among the lettuces. Photo Pam Dawling

Last July, when sheltering indoors from the heat, planning next winter and spring’s hoophouse crops, I researched and wrote up Controlling Aphids in Early Spring

I also have a post (another July information-gathering project!) about Insectary Flowers to Attract Beneficial Insects outdoors and in, at various times of year. At the end of April we sow several plug flats of different flowers to plant out in Insectary Circles at the ends of our outdoor raised beds. We hope to find a similar approach that will work earlier in the year for hoophouse and greenhouse aphids.

Ladybugs of Maine
Poster from the Lost Ladybug Project

Aphid predatory insects such as ladybugs, lacewings, aphid  parasites, damsel bugs, braconid wasps, rove beetles, syrphid flies, and spined soldier beetles are attracted to plants with small flat open flowers, like alyssum, dill, yarrow, buckwheat, sunflowers, and cosmos. This is a rather loose and general statement. On a big scale this is known as Farmscaping, and you can read about it in a publication from ATTRA; Farmscaping to Enhance Biological Control . You can use this publication to make a specific plan to tackle particular pests. Ladybugs are a good general help because they eat the eggs of many different pest species. Organic Integrated Pest Management from ATTRA gives wider information about managing pests organically.

 

Ladybugs of South Dakota
Lost Ladybug Project

eOrganic has many articles on Insect Management in Organic Farming Systems, that explain ways to tackle pest problems with ecologically-based practices, starting with actions chosen to reduce the chances of the pest ever getting a grip on your crops.

Aphids can get out of control in early spring in our greenhouse and hoophouse, as they become active before their native predators, such as ladybugs, emerge from hibernation. We have a particular problem in our hoophouse and in our greenhouse on the eggplant, pepper and tomato transplants from mid-April to mid- to late-May depending when we manage to get them under control. We are implementing our plan that we made in the summer.

Insectary flowers against aphids

Meanwhile in January we got bad aphids on the lettuce and, of our flowers to attract beneficials, borage was the only one flowering. It was not enough. We did three sprays of soapy water at 5 day intervals to kill the aphids.

Pepper plant with aphids. Photo Pam Dawling

There are many kinds of aphids. The lifecycle of aphids starts in spring with eggs hatching into wingless females that give birth via parthenogenesis to more females. Within a week, one female can produce 100 clones, which can repeat the process at the age of one week.  This continues until adverse weather or predators trigger production of a generation of winged female aphids that moves to new plants. Later in summer male aphids are born and females lay fertilized eggs that overwinter on host plants, to hatch the following spring.

This week, I want to give a progress report on the flowers we are growing. The chart gives details of the ones we chose, where we found the seed, and which months we decided to plant them in.

September-sown Borage flowering in our hoophouse in January. Photo Pam Dawling

The first planting, in September, was of borage and shungiku (Chrysanthemum greens) only. We hoped these would give us early flowers to start the program. Those plants became big enough to transplant in the ground and in 8” (20 cm) pots. We thought having some in large pots would enable us to move them to the trouble spots.

September-sown shungiku (chrysanthemum greens) in January.
Photo Pam Dawling

What I have noticed is that plants in pots dry out very quickly in both the hoophouse and greenhouse! The shungiku have looked close to flowering several times, and the accidentally dry conditions should have helped them to panic and bloom, but they haven’t. The borage flowered with pompom-like clusters, much more compact than spring outdoor borage does.

October-sown Meadowfoam plants in our hoophouse in January. Photo Pam Dawling

The second planting, in late October, consisted of Meadowfoam, Tidy Tips, Phacelia and Yarrow. Those plants are still small, as I write this at the beginning of February.

October-sown Phacelia in January. Photo Pam Dawling

They have been potted up from cells to 4” (10 cm) pots, and some are ready for bigger pots. No flowers, no help against January lettuce aphids.

October-sown Tidy Tips(and more phacelia) in our hoophouse in January.
Photo Pam Dawling

The third sowing has just happened, on February 1, and includes borage, shungiku, Meadowfoam, Phacelia, Tidy Tips and yarrow. I forgot to sow alyssum, so that will be a little later.

Slow-growing October-sown yarrow plants in January, using space in the path between lettuce beds. Photo Pam Dawling

The September-sown borage and shungiku both had some troubles with cold temperatures during January. We had a mild December, then a January with three non-consecutive nights at 10F (-12C). In our double-poly hoophouse, we roll out rowcover at night if it threatens to be 8F (-13C) or lower outdoors. That was about 6 times so far, but 10F (-12C) has been our coldest. Some of each of the borage and shungiku got cold-damaged, and some got rowcover-damaged (hasty pulling!)

So far, no beneficials have been seen on the borage flowers, and no aphids have been killed as a result. We’re still hopeful, especially about reducing aphid numbers on the peppers. More progress reports to come!

Flowers Against Aphids! Photo Pam Dawling

 

 

Workhorse Crops for February

 

White Russian kale in our hoophouse.
Photo Pam Dawling

This is my monthly series of 14 Workhorse Crops (asparagus, beans, cabbage, carrots, chard, collards/kale, garlic, potatoes, sweet corn, sweet potatoes, tomatoes, watermelons, winter squash, zucchini/summer squash). These crops are reliable and productive under a range of conditions. You can use the search box to find previous month’s entries, such as January.

At last the daylight is getting noticeably longer, although we still have very cold weather. We reach 10 hours of daylight on January 21, and 11 hours on February 20. In our hoophouse we are clearing crops before they bolt, and planting some quick crops before the warm weather ones go in in March and April. In the greenhouse we are starting seedlings and clearing lettuce that is thinking about bolting. Our seed orders are arriving and we are finishing up our various planting schedules and crop maps.

Workhorse Crops to Plant in February

Young carrots after their first thinning.
Photo credit Kathryn Simmons

Carrots

We sow carrots in mid-February, and again at the end of February. Yes, they take a long time to emerge when the soil is still so cold. But it’s a task we can get done now, and won’t have to do later, when we are busier. Carrots take 50 days to emerge at 41˚F (5˚C), (although of course it will have warmed up some before 50 days pass!); 17 days at 50˚F(10˚C); 10 days at 59˚F (15˚C); 7 days at 68˚F (20˚C); 6 at 77˚F (25˚C); 5 at 86˚F (30˚C) and don’t try hotter than that!

An EarthWay seeder, widely used for sowing small seeds like carrots.

We use an EarthWay seeder and the Light Carrot plate (although that still puts out lots of seed!) We can’t really justify the cost of a precision seeder like the Jang, for the amount we’d use it.

Asparagus

If you are planning to start a new asparagus patch, early spring is the best time to plant. This will give them as much time as possible that first year, to grow strong roots. The usual suggestion is to plant at least 10 crowns per diner.

Most growers purchase two-year-old crowns, although it is possible to grow your own asparagus from seed, if you can find seed of your preferred variety. The old OP varieties are still available, but newer all-male hybrids yield far more heavily, often more than twice as much. We chose Jersey Giant, a male hybrid resistant to asparagus rust and well-adapted to the mid-Atlantic. It produces big, tender, succulent spears each spring.

The best soil temperature for planting asparagus is 50°F (10°C) –  planting in cold soil encourages disease and offers no advantage. Remove shipped asparagus roots from the box as soon as they arrive, and untie the bundles. Don’t water them. If you need to store the roots longer than two weeks, spread them in trays or crates, in a cool, fairly dry place, until planting conditions are right. You can read more about growing asparagus in Sustainable Market Farming, and my recent article in Growing for Market magazine.

Asparagus photo by Kathryn Simmons
Indoor sowings for later transplanting outside or in the hoophouse

In our greenhouse we have started a couple of flats of fast-maturing cabbage. We like Farao (60d) and Early Jersey Wakefield (63d). Both numbers are seed to harvest. Subtract 20 days if counting from transplanting to maturity.

Open flats of cabbage seedlings. The nearer flat is a 3″ deep seed flat with four rows of seedlings.
Photo Pam Dawling

We have already sown our kale and collards for outdoor spring crops, in our hoophouse. Here’s the info on that: On January 24 we sow Vates kale and Morris Heading collards in the ground in the hoophouse, in the space recently freed up by the Chinese cabbage. For 1080ft outdoors, we need 108ft of seedling rows. We can fit 14 rows of seedlings across a 4ft (1.2 m) bed. We will transplant these outdoors as bare root transplants in mid-March.

Vates kale seedlings for bare-root transplanting.
Photo Pam Dawling

We don’t sow our chard and leaf beet until 3/24, because we want them for summer greens, after the kale, collards, broccoli and Asian greens have all bolted. But you can start them earlier, if you want earlier harvests. I’ll say more next month about chard, but if you want to get a start sooner, know that the seed will germinate from 41°F (5°C) to 95°F (35°C), and the best temperature is 86°F (30°C), when it needs only 4 days to pop up.

Hoophouse workhorse crops to plant in February

We do sow a few hoophouse greens successions during February, a row of snap peas, some lettuce mix, but nothing that qualifies as a Workhorse.

Workhorse Crops to Harvest in February

Russian kale, yukina Savoy and lettuce from our hoophouse.
Photo Wren Vile

Collards and Kale can be lightly harvested outdoors here in February. About once per bed during each of the coldest months, January and February. We’ll be able to harvest those beds once a week each in March. Our mnemonic for sustainable harvesting of leafy greens is “8 for later”, meaning we leave at least eight inner leaves when harvesting the outer ones, to ensure the plants have enough strength to regrow.

Overwintered Carrots and Cabbage are a possibility some years, but not this one! I actually prefer to get all our carrots safely harvested and stored, rather than have them still in the ground, where more things can go wrong! We have had 3 nights in January down to 10°F (-12°C), and I don’t think even Deadon cabbage would survive that many cold nights! Some of our Tadorna leeks are looking quite damaged. We don’t usually have that problem.

Hoophouse Workhorse Harvests in February

Bulls blood beet greens, chard, and some greens not in our Workhorse group, (turnip greens, Yukina Savoy, spinach) are still going strong. Our experimental carrots are still doing OK, although I’m not a fan of giving them hoophouse space for such a long time with no harvests. I notice I’m slipping into mentioning non-workhorses more often now the winter is biting us.

Red Russian kale in our hoophouse
Photo Pam Dawling

At last we can start harvesting our Russian kales in the hoophouse. We were late getting them established last fall, and growth has been slow. Now many of the other greens (Tokyo bekana, Napa cabbage, pak choy, the first tatsoi and the first mizuna) have all been eaten, we are very ready for the kale. Russian kale wilts easily and is best harvested into buckets as if a bouquet of flowers, with a little water in the bucket.

Workhorse Crops from storage in February

From storage in February we can eat carrots, garlic, potatoes, sweet potatoes, winter squash. Also frozen summer goodies, and pickled things, sauerkraut, pickled beans, and canned goods like salsa.

Workhorse Crops Special Topics for February: Phenology

Chickweed flowers.
http://ipm.ucanr.edu/PMG/S/W-CP-SMED-FL.006.html
Photo by Jack Kelly Clark.

I wrote about seed germination temperatures and phenology signs in April 2021. I have an earlier post about phenology here, and one about Harbinger Weeds of Spring.

Certain natural phenomena are related to the accumulated warmth of the season (rather than, say, the day-length), and by paying attention to nature’s calendar you will be in sync with actual conditions, which vary from year to year, and are changing over a longer time-scale.

You can learn when to plant by natural signs. For instance, we sow sweet corn when white oak leaves are the size of a squirrel’s ear. I got excited one weekend (April 10) when I saw wind-driven twigs on the ground with oak leaves definitely bigger than squirrels’ ears. But they were Red Oak, not White Oak.

Keeping your own phenology record is a useful guide to when to plant certain crops, and a way to track how fast the season is progressing right where you are. Phenology involves recording when certain wild and cultivated flowers bloom, seedlings emerge, or various insects are first seen. These natural events can substitute for Growing Degree Day calculations. Your phenology record will help build resilience in the face of climate change. Ours might be interesting to you, but unless you live in central Virginia, you can’t use our dates. You do need to make your own. This can be a great home-schooling project, or a crew I-Spy competition, or a calming end-of-day walk around your gardens.

Phenology Record

Dealing with winter weather in your hoophouse

December lettuce in our hoophouse after snowfall. Photo Pam Dawling

Dealing with winter weather in your hoophouse

We’ve just had Winter Storm Frida bring us a foot of heavy wet snow and, along with most of Virginia, several days without electricity. Six days in our case. Much longer, colder and snowier than I expected. I know, climate chaos makes predictions and expectations chancy! We are in zone 7a, with an average annual minimum temperature of 0-5°F (-18°C to -15°C) until recently.

In November 2018, I wrote a post for Mother Earth News entitled Dealing with Snow on your Hoophouse.

When the power goes out, close the air intake

Hoophouse air intake with a very useful flap to reduce or close the opening. Photo Kathryn Simmons

The first thing an operator of a double layer hoophouse should do when the power goes out (especially in winter) is to rush out and close the air intake. Without electricity to run the little blower, the air intake hole becomes an air outflow. Closing the flap on the blower stops the air escaping. In summer you might not mind, but in winter, the air between the layers of plastic maintains about 8F/5C warmer at night inside than outside, and plants can survive 14F/8C colder than they can outside, without extra rowcover; at least 21F/12C colder than outside with thick rowcover.

The “air bubble” also gives strength to the structure in withstanding loads caused by high winds or heavy snow. Soon after the power cut out on Monday morning, I set out towards the hoophouse. Then I remembered that when we changed the end wall plastic in the fall, we did not fit a cover flap. Worse yet, the air tubing projected out of the wall, making a hasty retrofitting impossible. I briefly considered “putting a sock in it” literally, but then pictured what would happen when the power came back on and sucked the sock into the motor, overheating it and starting a blaze. So, learn from our mistake – always fit a flap over the air intake!

Rolls of rowcover in our hoophouse ready to pull over the beds on very cold nights. Photo Wren Vile

We keep rolls of thick Typar rowcover at the ready and cover the individual beds if we expect the outdoor air temperature to be 8°F (-13°C) or lower. Otherwise we don’t use any inner rowcovers in our hoophouse. Without the insulating effect of the air bubble during the power outage, we decided to use the rowcovers when the outdoor temperature was going to be less than 16°F (-9°C). Several nights like that!

Perhaps this will be your first hoophouse winter. Some others will be remembering last winter, and hoping to find a better way of dealing with snow. Snow can be heavy stuff, so removing it is worthwhile. This can be done from the outside, pulling the snow down to ground level, and from the inside, bouncing the snow off the plastic. It isn’t necessary to remove all the snow. Once you have removed what you can, the daytime temperature inside the hoophouse will rise and help melt the rest of the snow. We have never needed to get out of bed in the night to tackle snow, but you might.

The Snobrum tool we use on the outside of our hoophouse.
Photo Pam Dawling

First we tackle the outside, or if snow is still falling or it’s frozen onto the plastic, we start with the inside. Either way, start with the south side, to get as much advantage from solar gain as possible. The important rule of snow removal is “First, do no harm.” Don’t make holes in the plastic in your efforts to remove snow! A hoophouse is most stable when the snow is evenly distributed. Since houses are stronger at the ends where they have end walls for support, it makes sense to start at the weaker middle and work in both directions if removing heavy snow.

Hoophouse snow scraping tool on a telescoping painter’s pole. (No snow in sight!) Photo Pam Dawling

For outside we use a tool (SnoBrūm™) which is sold for scraping snow off cars. It’s a foam board about 6″ × 18″ (15 × 45 cm) with a threaded insert that takes a telescoping pole. It is sold with a short pole, but a painter’s pole will give a much longer reach. If you haven’t yet got one of these handy tools, carefully use the back of a rake (wrapped in thick cloth). Pull the snow down between the bows, avoiding pulling the tool over the framework as much as possible, as that can easily make holes. Alternate with shoveling the snow away from the base of the hoophouse if the snow is deep (piles of snow pressing against the lower walls can do damage). Be careful not to hit the plastic with any metal tools. Don’t attempt to use the relatively fragile foam-board tool for pushing snow along the ground; keep it free of grit and use it only on the plastic.

Removing snow from a hoophouse at Dripping Springs Garden. Photo Mark Cain

Inside, don a visor (to keep blobs of icy water from landing on your face) and grab an old broom with its head covered in a cloth or bubble plastic, taped on. Make sure there are no sharp protrusions from the broom head. First walk along the paths nearest the walls banging the broom against the plastic. We find a double bouncing action works best, and we can get in a rhythm. This can be a long and tiring job! Start at waist height because if the lower snow falls down, sometimes the higher stuff will follow it down, saving you work. When you need to reach higher, tie or tape the broom to a longer stick. Or find something that screws onto your painter’s pole, such as a paint roller (!) and cover that with bubble plastic. Balance applying your energy with being gentle with the plastic. Do not use the foam-board scraper for bouncing snow — it will crack.

When you’re tired and no more snow is easy to move, wait and try again later. The warming effect of incoming daylight will help melt the snow next to the plastic, so that it is easier to start it sliding off next time you do the rounds.

Sometimes ice accumulates on the plastic. If you get freezing rain that sticks on the plastic, it creates a rough surface that keeps any snow that settles on top from sliding off until the ice thaws. The best way to remove ice is to melt it using warmth from inside. If you have double plastic and it is not windy, switch off the inflation blower — the heat from inside will reach the ice sooner. I recommend against breaking the ice free mechanically, as there is a big risk of the sharp edges of the ice cutting the plastic. You also risk abrasion every time you use a device on the outside of the plastic to pull snow or ice off the tunnel. This makes the plastic rough, and snow won’t slide off as well in the future.

Prevent Hoophouse Frame Collapse

Snow comes in various consistencies and weights. A foot (30 cm) of light fluffy snow may only contain as much water as 1″ (2.5 cm) of rain. But heavy wet snow can equal 1″ (2.5 cm) of rain in only 3″–4″ (8–10 cm) of snow. Each inch (2.5 cm) of rainwater-equivalent will load a structure with 5.2 lbs/ft2 (25 kg/m2). This is about 6.5 tons (5.9 metric tons) on a 25′ × 96′ (7.6 × 29.2 m) hoophouse! Uneven snow loads make a frame more likely to collapse because there are points of higher pressure. This happens if snow is thicker on one side of the hoophouse or if adjacent hoophouses are too close and snow piles up between them when it slides off the roof. The weight of snow can buckle the side of the frame.

Some growers have wood posts ready to wedge under the trusses for extra strength. It sounds like a good plan. Our hoophouse doesn’t have any crosswise trusses, just lengthwise purlins. It’s still standing after 18 years.

When heavy snow is predicted, turn a heater on a couple hours before the storm begins, with the thermostat at 70°F (21°C) or higher. The cost of the fuel is less than a new hoophouse. A portable propane heater (non-electric!) is a good thing to have on hand for unheated tunnels or if a furnace fails or if the power goes out. If you have a very heavy snowfall and it is not possible to remove the snow, then cut the plastic and let the snow fall into the hoophouse to relieve the pressure and save the frame.

“If this, do that”

We have an “If this, do that” card at the front of our hoophouse log book, to help with decisions. It divides snow events into three types.

  1. If the night temperature will be higher than 25°F (−4°C) and you expect less than 6″ (15 cm) of wet snow, leave the inflation blower on, go to bed and hope the snow will slide off.
  2. If the night temperature will be lower than 25°F (−4°C), or there will be more than 6″ (15 cm) of snow and no wind, turn off the blower until the morning, letting the interior heat do its best to melt the snow. If it’s going to be extremely cold, you’ll have to balance this with your need to keep your crops alive.
  3. If there is hard sleet or freezing rain, cycle the inflation off for three hours, on for three hours, with the goal of letting the interior heat melt some of the accumulation, and then using the inflation to push the slush off (give it some help in the morning). Repeat this cycle as needed.

Two great resources are Vern Grubinger, University of Vermont Extension, Prevent Greenhouse Collapse and the Rimol Greenhouses Blog How to Reduce Storm Damage to Your Greenhouse and High Tunnel.

In November 2020 I wrote Winter Preparations for Vegetable Gardens

Winter-Kill Temperatures

My annual blogpost of Winter-Kill Temperatures for Cold-Hardy Vegetables is always very popular. Usually searches for this info increase in October and peak in early November, when growers are deciding when to harvest each crop as the cold increases. In mid-winter you might consult the table to determine which crops to prioritize for extra rowcover if a bad thing happens.

I have learned that there is more damage when the weather switches suddenly from warm to cold. And that the forecaster in Raleigh, NC says it needs 3 hours at the critical temperature to do damage. Also note that repeated cold temperatures can kill off crops that can survive a single dip to a low temperature, and that cold winds, or cold wet weather can destroy plants quicker than simple cold.