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.
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.
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).
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 gmsows 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.
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!
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.
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.
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.
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
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.
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.
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.
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.
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.
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.
Fruit still available in May
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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!
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).
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:
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.
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.
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.
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.
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.
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.
If you don’t already have a crop rotation plan, this is the time to put one into place, especially if a lot of your ground is taken up with sweet corn every year! Our sweet corn occupies a lot of our space, so we pay attention to crop rotation. Corn is the only crop in the grass family that we grow, so this is not hard. We keep two or three years without corn between the corn years. Here’s the crop and cover crop sequence for each of our six sowings:
Sowings 1 & 2: The winter before the corn, we have a winter-killed cover crop of oats, (or sometimes a clover patch which has been growing all the previous year). Half the patch of this early corn is followed by oats in August and then garlic in early November. The other half gets oats and soy in August, to be winter-killed. This area will be easy to work up in early spring for our broccoli and cabbage.
Sowings 3, 4, & 5: The previous winter cover crop is winter rye or wheat with crimson clover (if we sow before 10/14) or winter rye or wheat with Austrian winter peas if after 10/15. The corn is followed by more rye or wheat and crimson clover in October. The following year we will plant potatoes here in June. The clover will have plenty of time to reaching flowering and therefore have plenty of nitrogen nodules on the roots.
Sowing 6: The previous winter cover crop is winter rye and Austrian winter peas. We undersow this corn with oats and soy. We mow high after harvest, and leave the oats and soy to grow until winter-killed. This patch is easy to prepare for our potatoes in March.
For the later sowings of sweet corn, a good stand of a preceding winter cover crop mix including legumes can provide all the nitrogen the corn needs (100-125 lbs/acre; 112-142 kg/ha). The nitrogen nodules on the roots contain the maximum nitrogen when the legume reaches its flowering point, so this method doesn’t work for early sowings.
No-till planting into strips tilled in a white clover living mulch sounds good but has been found tricky. Jeanine Davis addresses this in NCSU’s Organic Sweet Corn Production. The clover can out-compete the corn, become invasive and hard to get rid of. Soil temperatures will be lower (a disadvantage in spring) and slugs and rodents may increase. Trials of sowing corn into rolled and crimped hairy vetch are underway.
Undersowing (interseeding) cover crops such as white or crimson clover into the corn at the V5 or V6 stage is more successful. Ensure good seed-to-soil contact. The clover grows after the corn dies.
Some growers undersow with forage brassicas at last cultivation. Research shows this does not reduce corn yields. The forage can be harvested after the sweet corn harvest finishes.
Caring for Sweet Corn
Never allow soil in corn plantings to dry out, especially with close planting. You might need more than 1” (2.5cm) per week for maximum productivity, although corn is more drought-tolerant than some crops. The most important times for watering are silking (when the silks first become visible) and while the ears are filling out. We use overhead irrigation for corn, which works well to also water undersown cover crops.
Corn plants closer than 8” will compete with each other, so be sure to thin. People used to recommend removing the suckers that came from the base of the plant, thinking it led to higher yields. This has been tested, and in fact it can damage plants and possibly even reduce yields. (Reports from Clemson and Colorado State).
Sweet corn needs cultivating at least twice, at two weeks and four weeks after sowing. Even better are four rounds: at 7, 14, 21 days and finally one around 35 days when plants are 18-20” (45-50cm) high. Corn is shallow rooted so avoid deep cultivation. We use a walk-behind BCS tiller, followed by hoeing (and thinning at the first cultivation).
Each time we sow sweet corn, we wheel hoe or till between the rows of the previous planting, hoe and thin the plants to 8-12” (20-30 cm). We also till between the rows of the corn planting before that, hoe, and sow soybeans. Although they don’t supply the highest amount of nitrogen compared to other legumes, they are cheap, quick, somewhat shade tolerant, hinder weeds, and withstand foot traffic during harvesting.
While harvesting the corn we pull out any pigweed that has somehow survived our earlier efforts. Pigweed puts out its seeds in one big burst, so pulling up enormous pigweed is worthwhile, if it hasn’t yet seeded. Our soil has improved over the years, so it is now possible to uproot the 5ft (1.5 m) pigweeds. Sometimes we have to hold the corn plant down with our feet, but we do almost always succeed in getting the weeds out.
It is helpful to understand corn growth stages so that you know when the plant is most susceptible to damage, and when to take action. Corn growth stages are divided into vegetative (V) and reproductive (R). Stages are determined when at least 50% of the plants have reached or are beyond a particular stage.
Vegetative stages begin at emergence (VE), and each leaf with a fully developed collar is a new stage. Leaves within the whorl, not fully expanded and with no visible leaf collar, are not counted. Most sweet corn hybrids produce 18-21 leaves. Vegetative growth takes about 55-60 days after emergence. V3 (three leaf collars) begins 2-4 weeks after VE, and plants switch from using kernel reserves to photosynthesis and roots for nutrients.
Around V4, broadleaf weeds will stunt yields and should be removed. By V5, the numbers of potential leaves and ears are determined. Plants are 8-12” (20-30 cm) tall and the growing point may still be underground. Tillers (suckers, branches that grow from the lower five to seven nodes) appear.
V6-V8 –Beginning 4 to 6 weeks after VE, the growing point emerges above the surface, making the crop susceptible to frost, hail and winds. Beginning at about V6, the lower leaves may fall off naturally. At V7, rapid growth begins, and the number of kernel rows is determined. The number of potential kernels per row begins is set between V7-V16. By V8, the plant reaches 24” (60 cm) tall.
V9-V11 – At V9, tassels (not yet visible) and ear shoots are developing. New leaves appear every 2-3 days
V12 – The plant is 4ft (1.2 m) tall or more. Nutrients and water are important from this stage until the start of the R stages. The leaves are full-sized and about half are exposed to sunlight. “Brace roots” develop and the number of kernels per ear and size of the ear are set. Kernels can be damaged by insects and hail.
V15 – The plant is two weeks away from silking. Tassels are almost full-sized, but still hidden. Moisture and nutrient shortages now result in shorter ears and lower yields.
VT –Beginning 9-10 weeks after emergence, good pollination is essential to develop the kernels. Tassels are fully visible and silks emerge in 2-3 more days. Pollen shed begins, continuing for 1-2 weeks. Hail can be very damaging at this stage. Vegetative stages end when the corn develops a tassel (male flower). It takes about 20 days from tasseling to ripe.
R1 – The plant has silks outside of the husks and is at its most vulnerable. Environmental conditions can greatly affect pollination. The worst is drought, which dries the silk out, reducing its ability to collect pollen falling from the tassels.
R2 (“Blister”) stage – The kernels are filled with clear liquid. About 12 days after silking, the silks darken and dry out. Stress (especially drought) can cause kernels to abort.
R3 – Milk stage – About 20 days after silking, kernel fluid turns milky, as starch accumulates. The effects of stress are not as severe after this stage, but can still lead to shallow kernels.
R4 – Dough stage – About 26 days after silking, the kernels have a dough-like consistency. Stress can produce scrawny kernels.
The dent stage (R5) and full maturity (R6) will only happen if you leave the plant to produce seed.
Corn growth stages can be estimated using corn growing degree days (GDD), accumulated daily from the date of planting. GDD are calculated by averaging the max and min temperatures in a 24-hour period. 50°F (10°C) is subtracted from that average temperature to give the GDD for the day. A Corn GDD Tool is available at the High Plains Research Climate Center. Stress, especially drought, can affect growth and GDD alone may not provide an accurate estimate of growth stage.
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.
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.
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
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.
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.
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.
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.
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 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.
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.
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 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.
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).
Workhorse Crops to Plant in the Hoophouse in April: Squash, Cucumbers, Peppers
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.
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
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).
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.
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
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.
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.
When I was a new gardener at Twin Oaks Communityin central Virginia, I was a bit surprised to find the crew using peat moss in the potting mix. I come from the UK, where gardeners’ use of peat has long been challenged as unsustainable and ecologically destructive. I lived in Yorkshire and frequently took walks up on the “tops” (moors). I admit it did take me a while to come to appreciate the treeless stark beauty there. The moors are wild, wet and windy. You get wide views (if the mist or rain is not too thick). You get space and isolation, and tons of very fresh air. There are ancient trackways where salt and coffins were carried, and standing stones, and abandoned industrial workings such as millstone carving sites and mines. If you go alone, you need good navigation skills in the less-traveled parts. If you are unwary, you can find yourself thigh-deep in a bog, and the water is never warm.
In previous times, various efforts were made to drain the water and make the land arable or forested. Meanwhile, local people (or at least the “hearth-holders,” and I feel sorry for the others) had Rights of Turbary, meaning that each summer they could cut out slices of peat (turfs or turves) from the section of common or private land they had rights to, dry them and haul them home as winter fuel. More recently, interest rose in preserving the unique moorland ecosystems. The rich had their pheasant shoots, and they still do. The gamekeepers conducted controlled burns of the heather and bracken to make sure the plants grew tender new shoots at the time of year the young pheasants needed them. Sheep had some access. People enjoyed the birdlife, the heather flowers, the carnivorous sundew plants, the cottongrass, the mosses and other bog plants.
There are many types of peat moss, including 160 species of sphagnum moss. It grows slowly, and needs acidic water and cool-to-cold temperatures. It could be a renewable resource in places with very large amounts of untouched peat bogs, like Canada. That is, if we only harvest small amounts. But, oil and coal could theoretically be renewable if we wait long enough! The Canadian horticulture industry does have some guidelines and best management practices and a certification program for Responsibly Managed Peatlands. You can read about them in Jennifer Zurko’s article I describe later. There are some restoration projects, including the Moss Layer Transfer Technique, a kind of grafting or transplant process. The suppliers do have some “enlightened self-interest” in preserving their goose that lays the golden eggs. In 2021 in the UK, a phased-in ban on peat-based growing media will reach a complete ban in 2024. The rate of progress with phasing out sales was seriously set back when lots of new gardeners wanted peat during the Covid pandemic! Most retailers did not start phasing it out! The UK supply of peat is much smaller than in Canada, and the situation there is critical.
Relatively recently, many people have realized the enormous value of peat bogs as a big carbon sink. Keeping carbon in the ground is one way to strive to reduce the impact of climate change. The wet, anaerobic conditions hold the carbon in the dead plant matter. If we burn it, obviously the carbon is released. This is also true if we use peat in our gardens, mixing it with other ingredients and exposing it to the air. Peat is not coal, it’s not yet a fossil fuel, but it’s on its way. If you use peat, you may have noticed the old heather twigs, and leafy and mossy bits.
In a small country like the UK, it’s more obvious that the rate of use of peat exceeds the rate at which it is laid down. The UK is committed to limit or to completely stop peat use in the home garden market in 2024, and in the professional market by 2030. In the US, we import most of our peat moss from Canada, a large country with a relatively small population clustered close to the US border. Who sees the peat bogs? But the environmental impact is the same. Using peat moss contributes to global heating.
We reduced our use of peat moss at Twin Oaks by first discovering that our homemade compost could be screened (sieved) and used alone for potting transplants and sowing seeds in flats. Our remaining use of peat was for soil blocks. Soil blocks are cubes of potting media that can stand alone and grow seedlings. No plastic pots! To work in a soil blocker, the mixture must be quite wet and sticky. We experimented to find a recipe with as much homemade compost and as little peat moss as possible.
Next, we switched to replacing the peat with coir, the fibrous stuff from coconut shells. It is sold in compressed bricks that need soaking in water and crumbling before use. The material has been shredded, and is easy to use. This is a by-product of growing coconuts. No coconuts are harvested just for the coir. It seems like a freebie, a “waste” product. Maybe our purchase helps people in poorer countries to get more money for their agricultural efforts. Of course, getting the coir from the tropical coconut-growing regions does involve some shipping. It’s shelf-stable, so can come by ship, using less fuel than air transportation. However, maybe the coconut groves would benefit from the coir being returned to the soil below the coconut palms. There are no “wastes” in agriculture.
We still use coir for soil blocks, but we reduced our use of soil blocks, and last year made none at all. Now we use Winstrip trays instead of soil blocks. These are heavy-duty plastic with many years (decades?) of use ahead. They have square cells with vertical slits in the sidewalls and a staggered arrangement allowing air to prune the roots of the seedlings, one of the values of soil blocks. With Winstrip trays, we can use 100% home-made compost, not bought-in imports at all. Filling the Winstrips is very quick, much quicker than getting a good block mix and ejecting each set of four soil blocks.
Transplanting from Winstrips is almost as easy as transplanting soil blocks. With soil blocks, you open a hole in the soil (I used to like a right-angled trowel for this job; Eliot Coleman advocates a cut-off bricklaying trowel). Drop the block in the hole and firm the soil back in place. With Winstrips, you poke the plug up through the hole in the bottom, then lift it out, and it’s just like planting a soil block.
Margaret Roach addressed this issue with Brian Jackson, an expert in soil-less growing media on her website A Way to Garden: Can we Replace Peat Moss? You can read the interview or listen to the podcast.
The January 2022 issue of GrowerTalks magazine has an article from an industry perspective: Is Peat Sustainable by Jennifer Zurko. There is an archived version of an earlier webinar, linked from the article, if you prefer that format.
Suppliers of other potting media are selling ground composted bark and rice hulls. The same questions remain. In the case of rice hulls, the additional question is, do we want to aid and abet the eating of hulled white rice? And another is whether the potting mix has any nutrients for the growing plants. If you can make and use your own compost, you can be confident your plants will get nutrients. Commercial potting mixes have nutrients added. Making a change will involve assessing your options and the results you get. Using a different medium will require other changes, like how much you need to water. It will involve paying more attention than you needed for doing the familiar.
So, we are back to using (very durable) plastics and no longer buy any peat moss. Probably we won’t buy coir again either, once we have used what we have in stock. This is one of those agricultural dilemmas everyone gets to find their own solution to. Peat bogs can perhaps be restored eventually, but we need to then leave them be, and leave peat in the ground, as with coal and oil.
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
You need to specify a shipping date months ahead, then hope for good weather and no shipping delays.
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.
You have to get them all in the ground promptly, and do your best to keep them alive (because they arrive wilting).
Some amount of drooping (transplant shock) is normal.
Advantages of growing your own sweet potato slips
You can delay planting if the weather is all wrong (frost, drenching rain, heatwave)
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.
You can plant them in stages rather than all on one day.
You can grow extra and keep them on hand to replace casualties.
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.
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.
Three Successful Methods of Growing Sweet Potato Slips
Twin Oaks slips-in-flats method
Boutard single node cutting method
Hoophouse or caterpillar tunnel bedding method (Twin Oaks)
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.
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.
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!
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.
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:
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
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.
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.
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
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.
Another mid-March task for us is potato planting. I wrote a whole series about every stage of potato growinglast year. So I won’t say more here.
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.
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.
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 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.
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.
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.
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.
“Isn’t too cold for the predators to be around, Pam? unless they hibernated in the greenhouse. but even so, it’s still cold in there at night. We have some aphids too in the tatsoi and some of the lettuce, so thank you for all the tips, and the life cycle. I had not quite realized that the cycle was so short. I grow borage in the hoophouse but in the ground – the plants get large and gorgeous with clouds of blue flowers in March and April – much bigger and healthier than anything I try to grow outside. The honeybees absolutely love it and they attract are a lot of other insects too.”
Yes, it has been still too cold for predatory insects to be around, until this week, when ladybugs greet us around every corner. Our idea with the flowering plants was that by starting the plants in the fall, we’d have actual flowers earlier than if we started in “spring”, and that perhaps the extra stresses would even cause the plants to flower earlier. Apart from the borage, none of the others have flowered yet (Feb 23). We likely need to fine tune our sowing dates. We sowed at the very beginning of September and the very end of October. That two-month gap probably has better sowing dates! We noticed that some of our plants were not very cold-hardy. Some died and some had to be pruned of dead bits. Since then, we started more flowers in our greenhouse on February 1. Another thing we’re noticing since early February is that the plants in pots dry out very fast. It’s probably better to get the flowers in the ground in the hoophouse and greenhouse as soon as they are big enough, as suggested by the results of my reader quoted above, with borage.We had thought that having them in pots would enable us to move them into trouble spots.
Vegetable Crop Resources, Especially Weeds
A newly released handbook from Sustainable Agriculture Research and Education (SARE), Manage Weeds On Your Farm: A Guide to Ecological Strategies by Charles L. Mohler, John R. Teasdale and Antonio DiTommaso, is set to help us all. I haven’t read it yet (although I am looking forward to that!), so this is not a review, But these are three big names in weed science, and SARE is well-known for providing solid information on sustainable farming.
I had the great good fortune to attend a workshop by Chuck Mohler years ago, and got some realizations that forever changed my approach to weeds. Top of the list is that some weeds, such as pigweed (amaranth species), don’t distribute any seeds until they have grown very big. Until that point they are not threatening next year’s farming efforts. We used to get huge pigweed plants in our sweet corn, and fatalistically did nothing once we were in there harvesting, somehow believing it was “too late”. No, it’s not! They hadn’t seeded. We started to make a practice of pulling the huge pigweed every two days while harvesting corn. Often it was necessary to stand on the base of the corn plant to hold it in place, while pulling the weed. Then all we had to do was drop the pigweed between the rows. Sweet corn ripens in hot weather and the weeds soon died, rather than re-rooting. All those big leaves sucked the moisture right out of the plants. Be extra careful if you have spiny amaranth. We have twice eliminated this weed form our gardens, by diligent hand-pulling, only to have it reappear a few years later!
Conversely, galinsoga forms seeds very soon after germinating, while still small. This weed is one to strike early and repeatedly. It readily re-roots in damp soil. Our strategy when we are too late to hoe and have to hand-pull them, is to shake off as much soil as possible, then to either twist and break the stem (if there are not many), or “shingle” the weeds, laying them down with the roots of one on top of the leaves of the previously pulled plant, providing a surface of roots all exposed to the air, and none touching the soil. This works quite well. Timely hoeing is much better, of course!
Manage Weeds has chapters on How to Think About Weeds, Cultural Weed Management, Mechanical and Other Physical Weed Management Methods, Profiles of successful managers,and then the alphabetical rogues gallery of grass weeds and broadleaf weeds.
This book and all the online information from SARE is free of charge. You can buy print copies if that suits you better. Other good resources from SARE, while you’re at their website, include several other books: