No Visible Brassicas Month – Sustainable Market Farming

Unusual Crop for August: Kohlrabi

Harvested kohlrabi, Early White Vienna and Early Purple Vienna.
Photo McCune Porter

Unusual Crop for August: Kohlrabi

In May I wrote about Peanuts

In June I wrote about Bug-Resistant Summer Squash Substitutes

In July I wrote about Squash Blossoms and Other Edible Flowers

Much of this information comes from my book Sustainable Market Farming 2nd Edition.

This month, I’m writing about kohlrabi, an eye-catching and very storable brassica crop. Kohlrabi can be grown in central Virginia where I live in spring and in fall. In cooler climates it can be grown in summer, and in warmer ones through the winter. The winter-kill temperature for kohlrabi grown in the open, with no protection, is 15°F (–9.5°C), similar to red chard, Russian kales, and some varieties of beet, broccoli, cabbage. Kohlrabi production is like that of other brassicas, and the methods of cultivation and harvesting are very similar.

Kohlrabi is an unusual crop that is sure to attract attention at your market booth or be a discussion piece in CSA bags, in your garden and on your table. It is a swollen stem base, with leaves individually sprouting from the globe. When the tap root and leaves are trimmed off, it resembles a sputnik (the first manufactured Earth satellite, in 1957). It is tender and crunchy with a flavor between a cabbage and a turnip. It’s easy to grow and doesn’t wilt as soon as you harvest it. It can be eaten raw (sliced or grated) or cooked, and the leaves can also be cooked and eaten. It stores well, offering flexibility about when it is eaten or sold, which is always an advantage for growers.

Kohlrabi can be direct sown or transplanted, whichever suits you best.

Kohlrabi Crop Requirements

Brassicas grow best on fertile well-drained soil with adequate moisture. They require a lot of potassium, so a sprinkling of wood ash, kelp meal, or granite dust could be helpful if your soil is a bit short of potassium. Calcium, boron, iron, manganese, and molybdenum are also important for good brassica crops – healthy, biologically active soils can usually supply enough of all these. If not, amend as needed. Optimal growing temperatures for most brassicas are 60°F–65°F (15°C–18°C).

Green kohlrabi.
Photo Small Farm Central/Harvie

Cover Crops before Fall Kohlrabi

Because fall brassicas are transplanted in summer, it’s possible to grow another vegetable crop, or some good cover crops, earlier in the year. An overwintered cover crop mix of winter rye and crimson clover or hairy vetch could be disked in at flowering and followed by a short- term warm-weather cover such as buckwheat, soy, or southern peas, all before the fall kohlrabi. A spring-sown cover crop mix of bell beans (favas), barley, and oats does well before all fall brassicas at Roxbury Farm in New York, supplying all the nitrogen required by the brassicas, which are heavy nitrogen consumers. To minimize pests and diseases, don’t use brassica cover crops.

Rotations Including Brassicas

A rotation of 1 year in 4 is ideal for brassicas to avoid disease and pest buildup. When possible, plant one year’s brassicas at some distance from the previous year’s, rather than in adjacent plots. The spread of disease can be reduced by avoiding walking through wet crops and by controlling weeds in the brassica family, such as rock cress, pepperweed, garlic mustard, and wild rocket.

We always plant our kohlrabi in permanent raised beds as we cultivate these with a BCS walk-behind tiller and can work them a bit sooner than the flat fields, where we must wait for the soil to dry enough to use the tractor and disks.

Kohlrabi Varieties

Interest in kohlrabi is growing.I’m encouraged to see that Johnny’s now sells 7 varieties, Fedco has five, Baker Creek has 6 and High Mowing has 8!

We like the open-pollinated Early White Vienna and Early Purple Vienna (58 days from sowing) and the purple hybrid Kolibri (45 days), which is more expensive but beautiful, quick-growing, and uniform. Purple varieties seem slightly more resistant to cabbage worm and also less susceptible to cracking. A mixture of the white (green) and purple colors looks very attractive, and they’re both white under the skin, so our strategy is to grow 25%–35% purple and mix them in; 4 g = about 1,275 seeds, sows 135′ (41 m). 5,500–9,000 (avg. 6,500) seeds/oz, (200–320, average 230 seeds/g).

Superschmelz kohlrabi (60 days from transplanting) can also be summer sown for fall harvest. It produces 8″–10″ (20–25 cm) bulbs, which are an attractive globe shape and remain tender. The world record (variety not disclosed) weighed almost 97 lbs (44 kg), leaves included.

Kossak (80d to maturity) is a good storage variety that maintains its sweet, delicious, and tender dense white flesh in storage for 2–4 months.

The other type of kohlrabi is the slower-growing giant winter storage variety, such as Gigante (130 days from sowing in spring for late fall harvest). It regularly exceeds 10″ (25 cm) in diameter and 10 lbs (4.5 kg) in weight. Gigante’s crisp, white, mildly tangy flesh doesn’t get woody even when it gets enormous.

A September sowing of kohlrabi. Too late in the year to thin and grow to full-size, kohlrabi makes good salad and microgreens. Photo Bridget Aleshire

How Much Kohlrabi to Grow

We grow 360 row feet (110 m) of fall kohlrabi for a hundred people. We sow in mid-late July, and transplant around July 29–August 12 at 8″ (20 cm) apart in the row, with 9″–10″ (23–25 cm) between rows – 4 rows in a 48″ (1.2 m) wide bed. If direct sowing, you could sow in drills or in stations (groups of several seeds sown at the final crop spacing).

Systems for Growing Kohlrabi Transplants

The same systems you use for growing transplants in spring may also work well for fall: flats, cell-packs, outdoor nursery beds. We use an outdoor nursery seedbed and bare-root transplants because this suits us best. The nursery bed is near our daily work area so we’ll pass by and water it. (Our greenhouse is off to one side of our gardens.) We’re always relieved to close the greenhouse transplant season in May, as we no longer need to water little plants many times each day to keep them alive. Having the seedlings directly in the soil drought-proofs them to some extent; they can form deep roots and don’t dry out so fast.

Other people manage fine with flats in June and July, but we avoid it. If you use flats, it can help to have them on benches in an enclosed shadehouse, or outdoors, above the height of flea beetles. Ira Wallace of Southern Exposure Seed Exchange tells me 3′ (1 m) is high enough. Richard Jones, in his book Beetles, says flea beetles can jump at least 100 times their body length.

For our seedbeds, we use insect netting (ProtekNet) on wire hoops. In warm weather, I prefer netting against bugs because it lets in lots of air. Rowcover also protects against bugs, but provides less airflow, which can make the seedlings more likely to die of fungal diseases in hot weather.

Kohlrabi is a less-common brassica. This is Early Purple Vienna. Photo Kathryn Simmons

Germination of Kohlrabi Seeds

The most challenging part of producing fall brassicas is getting the seedlings growing well while the weather is hot. Unlike some cool-weather vegetables such as spinach, brassicas will germinate very well at high temperatures: the ideal is 77°F–85°F (25°C–29°C), but up to 95°F (35°C) works. Given enough water, summer seedlings will emerge in only 3 days. Once they have emerged, the challenge begins. As well as temperature and moisture in the right ranges, the seedlings need light (very plentiful in midsummer!), nutrients, good air-flow, and protection from bugs. Guarding the plants from bugs is the most challenging for us. We deal organically with flea beetles, harlequin bugs, and, sometimes, cabbage worms. Our main defenses are farmscaping and insect netting.

Search my previous posts for more on pest control. Brassica pests seem less interested in kohlrabi than in other brassicas, and as people are less likely to eat the leaves, there is room to tolerate a certain number of leaf-eating pests, while still having an attractive crop and a high enough yield.

“No visible brassicas” month

In an attempt to break the relentless lifecycle of the harlequin bugs, we now try to have a month from late June to late July with no brassicas visible in our garden. We make sure to mow down the spring broccoli trunks, the kale, and collards and harvest or pull up any other brassicas. We net new transplants and remove the netting a month later, allowing us to hoe and weed.

Brassica seedlings under Proteknet.
Photo by Bridget Aleshire

Timing for Fall Kohlrabi

Planting dates for fall crops can be exacting because the cooling weather slows down the plants’ growth, and a day or two delay in sowing date can mean a week or two delay in harvest date. Although it can be hard to think about sowing seeds in midsummer, it’s very worthwhile because brassicas develop delicious flavors as they mature in the cooler fall days,. Weeds and pests slow down then, too – once established these crops need little care.

The number of days to harvest given in seed catalogs is based on spring conditions – plants grow faster in warmer temperatures. To determine when to sow for fall plantings, start with your desired harvest date (noting when would be too late!), then subtract the number of days from seeding to transplant (21–28), plus the number of days from transplanting to harvest for that variety (given in the catalog description), plus the length of your ideal harvest period and another 14 days for the slowing rate of plant growth in fall compared to spring.

Example: Early White Vienna Kohlrabi, 58 days from sowing to harvest in ideal weather.

Consult https://weatherspark.com to estimate when it will get too cold in your location to leave kohlrabi in the ground. Here, in winter-hardiness zone 7a, our average annual minimum temp is 0°F-5°F (-15°C to -17.7°C), although most winters don’t reach those temperatures for very long. Our average winter low is about 25°F – 32°F (-4°C to 0°C).
Kohlrabi is hardy to 15°F (–9.4°C). The temperature is not likely to drop to 15°F (-9.4°C) before the beginning of December here.
Adding 40% more time, allowing 80 days, we could sow kohlrabi in early August and get a crop at the end of October.
Or mid-August for early November.
Or early September for the end of November or very beginning of December.
If you sow too late, use the seedlings for salad. Kohlrabi also makes a good microgreens crop.

Sowing Kohlrabi Seeds

Our rough formula for all transplanted fall brassicas is to divide our final crop row length by our in-row plant spacing and then sow extra to be sure of having enough good ones on transplant day. For kohlrabi to be planted 8″ (20cm) apart, to plant 360’ (110 m) we’ll need 540 perfectly lovely transplants.

We aim to sow 3 seeds/inch (1 cm apart). We make two sowings one week apart, to ensure we have enough plants of the right size. Each week after the first sowing, we weed the previously sown plants, and thin them to 1″ (2.5 cm) apart. We resow to make up the numbers if germination is low.

Young kohlrabi plants.
Photo Kathryn Simmons

Transplanting Kohlrabi

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

We transplant in late afternoon or early evening. We water the soil in the plot if it is dry, because it is very important at this time of year to get adequate water to the plants undergoing the stress of being transplanted. Likewise, good transplanting technique is vital. With drip irrigation, you can more easily give a little water in the middle of each day, which will help cool the roots. With only overhead sprinklers, you may not have the option of watering every day.

Kohlrabi Harvest

Harvest storage kohlrabi while the anchor (tap) root is still round, before it begins to elongate. We harvest our Vienna kohlrabi from October 20 to November 15. For storage cut off the tuft of leaves at the top of the plant and also the wiry root. It’s easiest to cut a disc off the bulb rather than try to cut through at the point between the bulb and the wire, where it is very tough.

Kohlrabi Winter Storage

Kohlrabi can be stored in a refrigerator or refrigerator-like conditions such as a CoolBot, 32°F–40°F (0°C–5°C), 80%–95% humidity. Basically Cold & Moist. Kohlrabi stores well in perforated plastic bags in a walk-in cooler. In a plentiful year, we have eaten stored kohlrabi throughout the winter into early spring.

Front cover of Beyond the Root Cellar book by Sam Knapp — Cover of Beyond the Root Cellar by Sam Knapp

A Few More Good Resources for Storage Information

Beyond the Root Cellar: The Market Gardener’s Guide to Growing and Storing Vegetables for Off-Season Sales and Food Security, by Sam Knapp
Johnnys Storage Recommendations https://www.johnnyseeds.com/growers-library/methods-tools-supplies/harvesting-handling-storage/storage-crops.html

Pests of the month in June: Mexican bean beetles and harlequin bugs

Our May bean sowing at the end of June.
Pam Dawling

Here’s the second in my new monthly series of posts, which will appear at the beginning of each month, until April 2026. This year the topic is insect pests and will feature the ones I’m most familiar with here in central Virginia. If you are in a different climate, you can use the Search Box on this site, where I have lots of mentions of insect pests when talking about the crops.

I’ll cover the worst pests we have each month, others that might also cause trouble, sustainable methods of managing those pests, and other good resources I’ve come across. All the crop chapters in the new second edition of Sustainable Market Farming also have sections about dealing ecologically with pests. If you also have good strategies, please leave a comment on this post.

Insect Pests in May covered cucumber beetles and squash bugs in detail, and Colorado potato beetles, eggplant flea beetles and leaf-footed bugs in passing.

Major Insect Pests in Vegetable Crops in June and some Management Strategies

Mexican bean beetles

For the Mexican bean beetle, the most effective solution is a non-native, non-frost-hardy parasitic wasp Pediobius foveolatus. As soon as you see the fuzzy yellow larvae of the MBB, call the Phillip Alampi Beneficial Insect Rearing Laboratory, New Jersey (call 609-530-4192 to consult with lab staff and order – avoid the weekend). Buy “mummies,” mummified parasitized MBB larvae, shrunken brown versions of the beasties eating your beans. If all goes well, you’ll only need to buy one unit. Some growers plant a small trap crop bean planting first, get those properly endowed with parasites and then sow bigger rows. Others club together with neighbors who grow beans and share out the parasites when they arrive. This is because they don’t come cheap, although they do come very effective! After about a week, you should see more shriveled brown mummies and you can relax. If you miss the initial sighting of the larvae, you can buy adult wasps, which multiply faster. Another source of the bean beetle parasite is Bugs for Growers.

Lifecycle of the Mexican bean beetle.
Photo Purdue University

An alternative to the parasites is to promptly flame the old rows of beans and start harvesting new rows.

We used to sow 7 times, every two weeks, and pull up the plants after two weeks of harvesting, when the bean beetles had made lacework of the leaves and were eating the pods. Since buying the parasitic wasps, we only need to make five sowings of beans through the growing season. The intervals between sowings shorten as the season advances. Plus, the beans are much prettier. For details of this method see my slideshow on Succession Planting

Succession Planting 2024 60 mins

Be sure that in your enthusiasm you don’t plan to sow beans too late in the year to get a worthwhile harvest. The formula to determine the last safe planting date for frost-tender crops such as green beans is to count back from the expected first frost date, adding:

the number of days from seeding to harvest,
the average length of the harvest period,
14 days to allow for the slowing rate of growth in the fall, and
14 days to allow for an early frost (unless you have rowcover – there is often a spell of warmer weather after the first frosts, and you can effectively push back your first frost date.)

With an October 14 frost date and a 50-day bean (and determination to put rowcover over the beans if we get a chilly spell), our last bean sowing goes in on August 3.

Asparagus beans are less damaged by Mexican bean beetles.
Peter Marks

If you’d rather avoid the problem of MBB, grow Southern peas (including asparagus beans), which are more resistant to MBB, or edamame (but watch for Japanese beetles).

Harlequin bugs

Harlequin bugs. Photo University of Maryland Extension Service

Reduce harlequin bug numbers in the spring as much as you can, or the fall problem will be huge! Harlequin bugs become a major pest here in June. When the spring broccoli harvest is over, bush hog all brassicas and start No Visible Brassicas Month to disrupt the harlequin bug lifecycle.

From late June to late July in our climate is the best time for having no brassicas accessible to insect pests. Use hoops and well battened-down netting or rowcover over all brassicas you don’t remove from the garden.

Harlequin bug nymphs on spider flower (Cleome); note, white flecks in the leaf typical of feeding by true bugs
Credit Missouri Botanical Garden

Harlequin bugs can sometimes be caught in worthwhile numbers in a trap crop of cleome (spider flower). Bend the infested flower heads over a small bucket of soapy water and knock the bugs off into the bucket.

We start sowing our fall brassicas for outdoor planting around June 26 and repeat a week later for insurance (July 3). The last date for sowing these crops is about 3 months before the first fall frost date. In our case that means July 14–20.

Consider the Days to Maturity of the greens you plan to grow, and remember that with fall crops, a delay of two days in sowing dates can delay harvests by two or three weeks because plants grow slower as days get shorter and cooler. You can’t make up for lost time!

Most brassicas will germinate faster at 86°F (30°C) than at 77°F (25°C), provided the soil is damp. But don’t expect much from cabbage, broccoli, collards or cauliflower above 86°F (30°C).

There are several strategies:

Direct sowing in the garden, in drills or in “stations” (groups of several seeds sown at the final crop spacing), is possible, if you have good irrigation. Large amounts of net or rowcover will be needed from day 1.
Sow indoors in flats, and when hardening off outdoors, it can help to have them up on benches, above the height of flea beetles. And netted against the harlequin bugs.
Sow outdoors in a nursery seedbed with hoops and Proteknet insect netting, as we do. Good airflow is vital—very thick rowcover or rowcover resting directly on the plants can make the seedlings more likely to die of fungal diseases in hot weather. Outdoor seedbeds and bare root transplants suit us best. The nursery bed is near our daily work area, so we’ll pass by and water it. Having the seedlings directly in the soil “drought-proofs” them to some extent; they can form deep roots and don’t dry out so fast.

Outdoor brassica seedling nursery bed. Photo Bridget Aleshire

We aim to transplant leafy brassicas at four true leaves (3-4 weeks after sowing). In hot weather transplant crops at a younger age than you would in spring – larger plants can wilt from high transpiration losses. This can be as little as 3 weeks after sowing. If we find ourselves transplanting older plants, we remove a couple of the older leaves to reduce the transpiration.

Cover transplants with hoops and netting or rowcover for several weeks, at which point the plants should be sturdy enough to withstand some bugs. The hoops will keep the netting up above the crops, preventing bugs from either feeding or laying eggs through the netting holes

Our fall brassica harvests are Sept 25 – late November for cabbage; Sept 10 – Oct 15 for our main broccoli harvest period, with smaller amounts picked either side of those dates. Kale and collards are harvested (by snapping off the bigger leaves) all winter in small amounts, and then in larger amounts as spring warms up, until the end of May, when they bolt.

Secondary Insect Pests in Vegetable Crops in June and some Management Strategies for those

Colorado Potato beetles

Colorado potato beetle on an eggplant leaf.
Photo Pam Dawling

Adult overwintered CPB emerge from the soil in spring and walk (they can’t fly at that point) to the nearest potatoes they can sense (how do they find them??). When you plan your garden, put your spring potatoes as far from the site of last year’s potatoes as you can. Give them a long, exhausting hike!

Monitor for Colorado potato beetles by walking diagonally or in a zig-zag through the patch once a week stopping at every fifth to tenth plant, counting the CPBs. Once you have counted about 5% of the plants (100 plants in our patch), average your findings to learn if you need to take action, or if you can simply wait another week.

Colorado Potato beetle late stage larva
Photo Pam Dawling

The CPB Action Level is if there are more than 50 adults/50 plants or more than 200 larvae/100 plants, (or more than 1.5 adults plus larvae per plant on average), or egg masses at more than 1 per 10 plants, or defoliation greater than 20%. The more accurate acceptable potato defoliation does depend how big the plants were to start with that week: 50-70% of top leaves on a 6″-8″ (15-20 cm) plant, 25% on 12″-16″ (30-40 cm), only 10% at full bloom, back up to 25% when full grown. Full bloom is the stage when the tubers are starting to form, therefore the most critical time for avoiding any setbacks.

If numbers exceed the Action Threshold, start daily handpicking or spray with Spinosad [or Neem]. We expect to need 1.5-2 hours and 9-10.5 galls for our 2200-2900 feet (670-884 m) of potatoes. Repeat if needed in 6-7 days. With Spinosad, which is a broad spectrum insecticide, it is important not to spray too much in any given year. When you monitor one week after your first spraying, take marker flags with you and flag the hotspots if the general state of infestation is not too bad. Then you could spot spray where larvae are seen, rather than respray the whole patch. Or you could check and handpick at those spots.

In mid-June we make a second planting of potatoes, as far from the first ones as we can manage. Because we mulch the second planting with hay, it does not get found by the CPB. In June the potatoes benefit from the thermal insulating and moisture-retaining effects of the mulch. In March we don’t mulch our potatoes because we want the soil to warm up some.

Miscellaneous summer vegetable pests

Thrips, aphids, maggots: Mow, do good crop cleanup.
Cucumber beetles: See May’s post. Cover cucurbits with ProtekNet and hoops immediately after sowing. Uncover once you start harvesting, to make life easier. You can then handpick the cucumber beetles or spray with Spinosad. Nasturtiums in cucurbit rows are said to repel They’ll look pretty even if they don’t work!
Nasturtium in a row of cucumbers.
Photo Bridget Aleshire
Squash vine borers are large caterpillars that chew into the main stems. They appear when the vines start to run. One strategy is to pinch the tips when vines are 1’–2′ (30–60 cm) long, causing multiple vines to grow, increasing the chance of some escaping damage. We are fortunate to not get much trouble with squash vine borers, but I know they can do major damage, living in the stems and eating their way upwards. To save the plant, at the first sign of trouble pick out the grub, then pile soil over the injury to help the plant recover. Injecting Bt (Bacillus thuringiensis) into the stem is another solution. Another approach is to make a collar of aluminum foil for each stem. There are pheromone lures for this pest too.
Squash bugs can do a lot of direct damage to leaves, and they also vector yellow vine disease. Plants attacked by squash bugs look baked to a crisp, with curled bronzed leaves. Destroy the gold eggs spaced out on the underside of leaves, by tearing off the infested pieces of leaf and crushing them. Set out boards overnight to trap the bugs; they congregate under the boards, and you can squash them in the morning. Moschata varieties are the best ones for regions with high levels of squash bugs.
Leek moth larva
Photo Wikipedia

The leek moth is moving south from Canada. It makes pinholes in the leaves and tunnels into the material of the leaf, causing damage similar to tunneling by leaf miners. Leek moths lay individual eggs on lower leaf surfaces once night temperatures are above 50°F–54°F (10°C–12°C). See the Ontario Ministry of Agriculture, Food and Rural Affairs for more information. Insect netting on hoops can be used. Consider an allium-free month in summer if you don’t grow leeks, in winter if you don’t grow garlic.

Leek moth damage on leaves of mature leeks.
Photo Wikipedia
Others include the pea curculio, stink bugs, loopers, bean leaf beetle, potato leaf-hopper, seed corn maggot, European corn borer, tarnished plant bug, mites, slugs, root lesion nematodes. Any may plague you. Consult reputable online sources, or your Extension Service.

Keeping on top of fast growth rates – Special Topic for June

Mow all paths and edges weekly. This will help protect your crops from the new season’s grasshoppers, as well as rabbits, groundhogs and deer. We don’t want to provide them with cover. Mowing will also reduce the formation of weed seedheads, and perhaps your grass allergies.

Till in finished crops promptly. Flame if tilling is impossible or you want to minimize tilling. At least mow the old crops down. This will reduce the habitat and food for pests. Alternatively, pull the old crops, load them onto a garden cart and take them off to your compost pile.

Be aware that removing a pest-infested crop (without roasting the pests) can scatter the pests to other nearby crops. Flaming is a good method of dispatching bug-infested old crops, and has the advantage of minimizing tilling. Consider leaving a sacrificial cluster of the old plants growing overnight, and then flaming them in the morning.

Next month I’ll write about corn earworm, cutworms and tomato hornworms.

More Resources

eOrganic Insect management in Organic Farming Systems has a long list of dozens of short publications, including specific ones for Striped Cucumber Beetle, Squash Vine Borer, Squash bugs, Stink bugs, Aphids, Nematodes, as well as Scouting, Farmscaping

Using Native Flowering Plants to Attract Beneficial Insects. Altieri, M., C. I. Nichols, and M. A. Fritz. 2005. Manage insects on your farm: A guide to ecological strategies. Sustainable agriculture network handbook series book 7. (Available online at: http://www.sare.org/Learning-Center/Books/Manage-Insects-on-Your-Farm)

ATTRA Squash Bug and Squash Vine Borer: Organic Controls, by K. Adam, includes pest lifecycles, systems-based management practices, mechanical and physical practices, and biological and botanical controls

Success with winter kale and collards

Alabama Blue collards.
Credit Southern Exposure Seed Exchange

July/August is the time we sow kale and collards for overwintering. (My whole Cooking Greens of the Month series of posts mentions kale and collards frequently!) Our kale harvests can start October 1, collards Oct 15. If we have planted the right amount, we can harvest each bed once a week in October, November, December, March and April, and once a month in January and February. As the weather starts to warm, production picks up, and we can harvest until the crops bolt at the end of May.

Kale and collard crop requirements

Here in central Virginia, most brassicas are planted in spring and again in fall. Although it can be hard to think about sowing seeds in midsummer, it’s really worthwhile to grow fall brassicas because as they mature in the cooler fall days they develop delicious flavor. Weeds and pests slow down then, too — once established these crops need little care. And will feed you all winter.

The most challenging part of growing fall brassicas is getting the seedlings growing well while the weather is hot. Unlike some cool-weather vegetables such as spinach, brassicas can germinate very well at high temperatures: the ideal is 77°F–85°F (25°C–29°C) for kale, 77°F (25°C) for collards, but up to 95°F (35°C) works. Some people find refrigerating the damp seeds for 24 hours gives a better germination rate. Given enough water, summer seedlings will emerge in only three days. Once they have emerged, the challenge begins. As well as temperature and moisture in the right ranges, the seedlings need light (very plentiful in midsummer!), nutrients, good airflow and protection from pesty bugs. Guarding the plants from bugs is the most challenging for us. We deal organically with flea beetles, harlequin bugs and, sometimes, cabbage worms. Our main defenses are farmscaping and insect netting.

Vates kale in the fall.
Photo Bridget Aleshire

Rotations with fall brassicas

Because fall brassicas are transplanted in summer, it’s possible to grow another vegetable crop, or some good cover crops, earlier in the year. An overwintered cover crop mix of winter rye and crimson clover or hairy vetch could be disked or tilled in at flowering, and be followed by a short-term warm-weather cover such as buckwheat, soy or southern peas. A spring-sown cover crop mix of bell beans (favas), barley and oats does well before all fall brassicas at Roxbury Farm in New York, supplying all the nitrogen the brassicas need. Brassicas are heavy nitrogen feeders. To minimize pests and diseases, we don’t use any brassica cover crops, ever.

Systems for growing collards and kale

Direct sowing, in drills or in “stations” (groups of several seeds sown at the final crop spacing), is straight-forward. We do this with our fall kale. Or try the same systems you use for growing transplants in spring. If you use flats, it can help to have them on benches in an enclosed shade-house, or outdoors, above the 3′ (1 m) height that flea beetles can jump.

Other people do well with flats in June and July, but we avoid it. We use an outdoor nursery seedbed and bare root transplants for collards and most of our fall brassicas, because this suits us best. The nursery bed is near our daily work area, so we’ll pass by and water it. (Our greenhouse is off to one side of our gardens.) We’re always relieved to close the greenhouse transplant season in May, as we no longer need to water little plants many times each day to keep them alive. Having the seedlings directly in the soil drought-proofs them to some extent; they can form deep roots and don’t dry out so fast.

Brassica seedlings under ProtekNet in August.
Photo Pam Dawling

For the seedbeds we use insect netting (ProtekNet) on wire hoops. Rowcover can make the seedlings more likely to die of fungal diseases in hot weather — good airflow is vital. In warm weather, I prefer netting to keep bugs off, because it lets in lots of air.

“No visible brassicas” month

In an attempt to break the relentless lifecycle of the harlequin bugs, we try to have a month from late June to late July with no brassicas visible in our gardens. We make sure to mow down the spring broccoli trunks, the kale and collards, and harvest or pull up any other brassicas. We ensure that our fall brassica seedlings are grown under ProtekNet Pest Control Netting, and we net them as we transplant them. We remove the netting a month after transplanting or sowing.

Timing of kale and collard sowings

The number of days to harvest given in seed catalogs is usually based on spring conditions — plants grow faster in warmer temperatures. We sow collards July 5 and 12. The last date for sowing is about 3 months before the first fall frost date. In our case that means July 20.

Vates kale under ProtekNet. Photo Bridget Aleshire

For kale we use a mixed direct-sow/transplant method that allows for patchy germination, and requires less watering than if direct sowing it all. Three times, (8/4, 8/10, 8/16), we sow two beds with rows 10″ (25 cm) apart and net them. We water them daily until we can see good germination, which is not coincidentally the date for the next sowing.

When the plants have several leaves, we carefully thin them, leaving one plant every foot (30 cm). We use the carefully dug thinnings from those beds to fill gaps and to plant other beds, at the same plant spacing. A reason we like this system is that we want a lot of kale, and there isn’t time to transplant it all.

Planning for kale and collards

In February we make a more detailed plan for the fall brassicas and draw up a spreadsheet of how much of what to sow when.

Kale and collards, our most winter-hardy brassicas, are grown in our raised bed area, which is more accessible for winter harvesting. Each bed is 90′ x 4′ (27.4 x 1.2 m) and fits four rows of most crops, but only three of the bigger collards.

Sowing kale and collards

Our rough formula for all transplanted fall brassicas, such as our collards, is to sow around a foot (30 cm) of seed row for every 12’–15′ (3.6–4.6 m) of crop row, aiming for three seeds per inch (about 1 cm apart). This means sowing 36 seeds for 10 plants grown on 18″ (46 cm) spacing. And we do that twice (72 seeds for 10 plants!), two sowings a week apart, to ensure we have enough plants of the right size. Each week after the first sowing, we weed the previously sown plants, and thin them to one inch (2.5 cm) apart. Then we check the germination, record it and resow to make up the numbers.

Transplanting collards and kale

We aim to transplant most brassicas at four true leaves (three to four weeks after sowing), but it may slip to five weeks before we get finished. It is better to transplant crops at a younger age in hot weather than you would in spring, because larger plants can wilt from high transpiration losses. If we find ourselves transplanting older plants, we remove a couple of the older leaves to reduce these losses.

We plan to transplant for an hour and a half or two hours in late afternoon or early evening daily, until done. We water the plants ahead of time, and also the soil in the bed if it is dry, because it is very important at this time of year to get adequate water to the plants undergoing the stress of being transplanted. Likewise, good transplanting technique is vital. Water a lot more than you do in spring. If you have drip irrigation, you can more easily give a little water in the middle of each day, which will help cool the roots. With only overhead sprinklers, you may not have the option of watering every day.

For the first few weeks after transplanting, we use wire hoops to support netting to keep the bugs off. Do not float insect netting directly on the plants, as you might do with rowcover: The females are able to land on the netting and lay eggs through the holes. Insects with small mouthparts can bite the leaves through the mesh. Setting out drip tape, watering the soil before planting and setting the plants by an emitter all help survival during the hot summer days.

We plant kale by a mixed direct-sow/transplant method that allows for the possibility of patchy germination, and requires less watering than if we direct sowed it all. We sow two beds on each of three dates, Aug 4, Aug 10 and Aug 16. with 4 rows 10″ (25 cm) apart, and net them. Later we carefully thin them, leaving one plant every foot (30 cm). (We grow Vates, a dwarf variety.) Those plants grow quicker than transplants, as they have no transplant shock. We use the carefully dug thinnings from those beds to fill gaps and to plant more beds, at the same plant spacing. A reason we like this system is that we want a lot of kale, and there isn’t time to transplant it all. Vates kale is the hardiest variety we have found, although I’d love to find a taller Scotch curled variety that could survive our winters (Winterbor does not survive as well as Vates).

Morris Heading Collards. We plant 3 rows in a 4ft wide bed. Photo Kathryn Simmons

Collards are transplanted bare-root, from the nursery bed. We plant two beds of collards, and they have a wide spacing, so there are not many to transplant. We plant at 18″ (46 cm) in the row, with rows a foot (30 cm) apart (three rows per bed).

Caring for fall kale and collard crops

Aftercare for kale and collards is a simple matter of hoeing, weeding, watering as needed and watching for pests.

Two weeks after transplanting the collards or sowing the kale (late August–early September), we open the netting, hoe or wheelhoe between the rows, and recover the plants. Four weeks after transplanting or sowing, we pack away the netting, hoops and sticks we use to hold down the edges, and cultivate again between the rows and around the plants in the row. For overwintering brassicas grown “on the flat” in the field, we undersow with a clover mix at the second cultivation. You can read about this in my book Sustainable Market Farming.

We do not normally use rowcover in the winter for kale and collards, as they will survive here in Zone 7a without. In harsh winters we lose the collards. Using rowcover would keep crops in better condition later into the winter, and increase the yields, but we have found rowcover fibers stuck in the curly-leaved kale. We don’t like the extra work of dealing with the rowcover, but your situation may warrant it.

Nancy Malone Wheat purple collards with frost. Credit Southern Exposure Seed Exchange

Harvesting kale and collards

Kale and collards are harvested all winter by snapping off the bigger leaves in sustainable amounts. Be careful never to overharvest, or the plants will be stunted and unable to recover to a productive level. For most leafy greens in winter, our mantra is “Leave 8 for Later”, meaning that until you develop an eye for sustainable harvesting, count out from the very center of the plant, being sure not to pick any of the innermost eight leaves. If you can leave one or two more leaves, do so, as more foliage leads to more photosynthesis, which leads to more foliage!

White Russian kale in our hoophouse in February. The Russian kales are not as cold-hardy as Vates. Photo Pam Dawling

Red Russian kale in our hoophouse in February. The red kales d not grow as big as green ones. Photo Pam Dawling.

In January, note if you have grown enough or more than enough for your needs, and plan next year to get closer to just the right amount.

Cooking Greens in August

The vine tips of sweet potatoes make good summer cooking greens.
Photo Bridget Aleshire

Cooking Greens to Harvest in Central Virginia in August

Chard leaves and sweet potato vine tips can be harvested here all month. It really isn’t the season for new cooking greens. We have cabbage in storage, to get us through the “dead center” of the summer, until we can start the fall green harvests. In late August we can start to harvest senposai, turnip thinnings, Yukina savoy, komatsuna, Maruba Santoh, pak choy, Tokyo Bekana. Turnip thinnings can make a tasty dish, if the small plants with marble-sized turnips are cooked together with their attached tops. Wash well, of course.

If we had grown them, we could harvest molokhia (Egyptian spinach, related to okra), manihot (aibika, also related to okra), and okra leaves themselves, if the Japanese beetles have left enough! See the special topic below for more on these.

Cooking Greens to Sow in Central Virginia in August

We sow our fall brassicas weekly throughout late June and July – see the Special Topic for June for all the details. If we have had big trouble, we might need to resow some broccoli, cabbage, or Asian greens in August, but hopefully not. If we do need to resow this late, we choose only the fast maturing varieties, to make up for lost time.

Although sowing the fall greens in nursery seedbeds comes to an end, we are not slacking. August is our month to establish 6 beds of Vates kale. We use ProtekNet against flea beetles. Our method is a hybrid between direct sowing and transplanting. With over 2160 row ft (660m) to establish in the sometimes brutally hot and dry conditions, we would not want to transplant this number of plants. Direct sowing all at once would be impossible for us to keep sufficiently watered. We focus on two neighboring beds (720 row ft, 220m) at one time. We direct sow the two beds, cover with netting, and water by hand every day. In 4 days the seedlings will have emerged, and they can survive on less than daily watering after 6 days. So every 6 days we sow two beds. Our dates are August 4, 10, and 16. Sometimes we sow by hand, sometimes with the EarthWay seeder, with plate 1002-24. Our last date for this round of sowings is September 7.

On August 20 we revisit the first two beds and resow if the survival rate is really poor, or we plan to move plants around to fill gaps, if there are not too many. On August 24 we revisit the second two beds and resow sections if needed. On August 28 we revisit the last pair of beds sown. Our last date for resows is September 15. We only grow one variety outdoors, and we can use plants from any of the beds to fill out any other. We tackle this task when the plants are about 3-4 weeks old, in late August and early September. We eat the extra plants.

We grow Vates kale, a very cold-hardy dwarf Scotch curled type. I’d love to find a bigger equally-hardy curled variety, but I have not found any. We don’t rowcover our outdoor kale, so it needs to be very hardy. We tried rowcover one year, but it was a bother to deal with, and fibers of the rowcover caught in the curly leaves and we were not appreciated by the cooks.

For the second pair of beds, we often repurpose the first of our brassica seedling beds, as the broccoli, cabbage and Asian greens are all planted by then, the bed has clean soil, and netting and sticks at the ready.

Thinned turnip seedlings.
Photo Pam Dawling

We sow turnips from early August to mid-September, and beets from early August to late August, for both roots and greens. It is hard to get beets germinated in hot soil, but if you delay, they don’t have time to grow big roots before the cold weather. You can sow beets dry or presoak 1-2 hours (not longer, and not in too much water, as they easily drown); sow 1/2″-1″(1-2.5cm) deep, tamp the soil, keep the surface damp, water daily for the 4-6 days they take to emerge. We use netting for turnips, but not for beets, unless the grasshoppers are bad.

It’s also possible in warmer areas to sow Swiss chard or leaf beet for a fall crop. This is a useful Plan B if some other crops have failed. The last planting date is ten weeks before frost. Our average first frost here is October 20. This is an average over the past 13 years. We can only sow chard until August 11 or so. It’s not that the first frost will kill the chard, far from it, but the frost date is an indicator of when growth starts to slow down.

Cooking Greens to Transplant in Central Virginia in August

Morris Heading collards.
Photo Kathryn Simmons

June is the time to prepare a plot for the fall broccoli and cabbage. July and August are the time for transplanting them. See the July cooking greens post for details of how we tackle this big transplanting job. In early August (if not done in late July) we transplant two beds of collards. By late August we want to really finish transplanting the fall broccoli, cabbage, and the kale from the August 4 sowing.

In week 7 of our fall greens schedule (the first week of August): We transplant week 4 sowings of senposai, Yukina Savoy, and anything we resowed in week 4. We also fill any gaps in week 4 transplantings (= week 1 sowings). Cover: hoop and net or rowcover.

In weeks 8 & 9 (the second and third weeks of August): We transplant anything we didn’t keep up with, and replacements in weeks 5 and 6 transplantings (weeks 2 & 3 sowings), Cover: hoop and net or rowcover.

Other Cooking Greens Tasks in Central Virginia in August

Broccoli undersown with clover.
Photo Nina Gentle

If things are on schedule and we haven’t needed to replace many casualties in the big brassica patch, we roll and store the covers, wheelhoe or till between the rows and weed. Then we undersow with a broadcast mix of mammoth red clover, white Ladino clover, and crimson clover. This will become our all-year green fallow next year.

August is our worst month for grasshoppers and crickets, so we watch for them and either use netting, or postpone sowings until the end of August.

To improve germination next month, we put spinach seeds in the freezer now, for at least two weeks.

No visible brassicas month comes to an end. To disrupt the lifecycle of the voracious harlequin bugs, we have only netted brassicas in our gardens from early July, when the last of our spring brassica crops get mowed down and disked in, and we sow seedling brassica crops under netting. When we transplant the young brassicas, we cover those all with netting or rowcover for a few weeks.

Special Cooking Greens Topic for August: More Unusual Hot Weather Cooking Greens

See Cooking Greens in July for details about the chenopods – amaranths, Aztec spinach, orach, Good King Henry, Magenta Lambsquarters, strawberry beet and also celosia. Many of these can be sown again in August to provide a succession of tender young greens. Here are some other hot weather greens. Like July’s unusual cooking greens, all the following are warm weather crops, so don’t try to grow these in early spring or into late fall. If sown in August, they can follow an earlier crop such as lettuce, peas, or early sowings of beans, squash or cucumbers.

Sweet Potato Leaves, Ipomoea batatas

Plant sweet potatoes for a fall root harvest, and get the bonus greens crop all summer! You can harvest the leaves and young shoots for cooking greens at any time during growth (just don’t take too much at once). For cooking ideas, find Water Spinach recipes and substitute sweet potato shoots. Chili and shrimp or peanut sauce feature in many recipes.

Water Spinach, Ipomoea aquatica; aka Kang Kong, Ong Choy, Phak Bung.

This tropical, semi-aquatic plant is cultivated for its tender shoots and leaves. It is easy to start from seed or you can root cuttings (roots show in 2-3 days) from bunches bought at an Asian supermarket. The long stems will readily root from the nodes. The leaves are quite large: 2”-6” by 1”-3” (5-15 by 2.5-7.5 cm). The tender shoots are cooked along with the leaves. The flowers look just like sweet potato flowers. It is a USDA Class A noxious weed in Hawai’i, Florida and California, where it has escaped into the wild. Check your state regulations, and grow this in some sort of container to be sure. A safer bet is to eat sweet potato greens instead.

New Zealand Spinach (Tetragonia expansa, Tetragonia tetragonioides)

New Zealand Spinach tolerates heat and drought beautifully. It is salt-tolerant and will even grow in sand. This sprawling bushy plant with small, succulent, triangular leaves is generally free of pests. The flavor is very mild, not particularly like spinach, despite the name.

Soak the seed for 4-24 hours before planting to speed germination – it can take 8 weeks to emerge. Direct-sow from mid to late spring (bean-planting time), or sow indoors about 6 weeks before last frost. It takes 65-75 days to maturity. Thin to at least 6” (15 cm) apart. It needs hot weather to really get going.

Regular trimming encourages lush growth. Use scissors to harvest the shoot tips. Picking the individual triangular leaves would be tedious, as they are fairly small.

Like true spinach, Tetragonia leaves contain oxalic acid, so should be eaten in moderation, mixed with other greens.

It can become invasive as it sets seed readily. This happened to me the first year I grew it – I thought some self-sowing would be a good thing, but I seriously under-estimated both the number of seedlings I’d get and the distance the seeds could ping.

Red Malabar Spinach.
Photo Southern Exposure Seed Exchange

**Malabar Spinach (Basella alba, Basella rubra)**

This tropical plant is from Asia and Africa.. The gorgeous twining vines are very tall, so they need to be trellised or caged, which has the bonus of keeping the leaves clean. One technique is to plant them on the pea trellises and let them take over as the peas finish. There is a green-leaved Malabar spinach with red stems, but the red is exceptionally beautiful, so I recommend that one. This crop also does well in partial shade.

The crinkled heart-shaped leaves look like spinach, although more crisp, glossy, and slightly succulent. They have a flavor similar to beet greens. They stay mild and maintain healthy growth all summer. Bees love the blossoms.

Sow in late spring, when it’s warm enough for beans. Germination is slow – even at their preferred temperature of 70-80°F (21-27°C) the seeds can take 10-14 days. Soaking the seed in warm water before sowing may help. You could start them indoors and transplant at 3-6 weeks old, or older, as much as 8” (20 cm) tall. Plant or thin to at least 6” (15 cm) apart and, to promote a more branched plant, pinch out the central shoot after the second set of leaves.

The plants need 60-90 days to maturity, and then will produce an abundance of moderately small leaves all summer, until cut down by the slightest frost. Harvest individual leaves as needed, or cut the vine tips to use as cooking greens. (Young leaves can be added to salad mixes.) Lop the vines when they are as tall as you want to deal with – they will regrow even if severely cut back.

The taste is slightly seaweedy (it’s also known as “land kelp”), and the texture is somewhat mucilaginous in the way that okra is. It can be eaten raw if you like the chewy texture. It is excellent for stir-fries or for thickening summer soups and stews. William Woys Weaver reports that it cooks beautifully in a microwave, but on a hot day eat the refreshing leaves raw. The leaves store for up to two weeks in the refrigerator.

This crop is pest-free, but watch out for the staining properties of the black berries (good for dying fabric). Malabar spinach does self-sow, but this is only likely to be a problem for those in tropical climates

Okra leaves

Yes, okra ;eaves are edible.
Photo Bridget Aleshire

Yes, okra leaves are edible. See Chris Smith’s amazing book The Whole Okra

Egyptian Spinach, Corchorus olitorius (Jute, related to okra)

Aka Melo Khiya, Molokheiya, Molokhia and similar attempts to render the Arabic name in our alphabet. This Arabic summer cooking green grows well in Virginia, North Carolina, Florida, Texas and everywhere with hot summers.

This versatile, continuous-harvest vegetable can survive both dry and wet conditions in warm or hot weather. GrowerJim has good details.

Only the small leaves are cooked and eaten. The dried leaves can be used to thicken soups or for tea. It’s not a vegetable to be eaten alone in big cooked heaps – it’s just too mucilaginous.

Jute fiber is extracted from the mature plants, suggesting a) don’t try to eat over-mature plants, and b) paper-making and various fiber arts could be in your future.

Depending on your climate and preferences, you can direct sow fairly heavily and thin, or start seeds in flats and transplant 12″ (30 cm) apart in all directions. Plant after danger of frost is past and the soil is warming steadily. Egyptian Spinach likes full sun, warm to hot weather and steady moisture – mulch will help keep the soil moist.

It takes 70 days to maturity, then holds well in the field, providing several cuttings. If you prefer to harvest the whole plant, succession-sow for future supplies. Continue to give compost or nutrients throughout the season, to encourage tender new growth.

It grows 2’-3′ (60-90 cm) tall or more, and then bears yellow flowers if you don’t keep it clipped back. The flowers are followed by seed pods which are edible and tasty when young, with more flavor than the leaves.

The mature seeds can be saved for replanting. Seed is available from Sandhill Preservation and Bountiful Gardens (who reassure buyers that the seed is naturally green in color and is not treated.)

Manihot (aibika, Sunset hibiscus, also related to okra) Abelmoschus manihot – (L.)Medik.

It is a hardy perennial in US zones 8-11. Green Harvest has growing information. Plants for a Future also. Seeds are sold by Monticello as an ornamental, but Floral Encounters say: “However the importance of this plant is that it is one of the world’s most nutritious leafy vegetables because of its high protein content.”

Squash leaves and shoots, Cucurbita spp.

If your squash are being too rambunctious, or you are thinning a row a bit late and have sizeable plants, consider a harvest of vine tips and leaves. Or grow some just for this purpose, if you need a quick-growing summer green with novelty appeal. Stir-fry or gently braise – good with eggs for breakfast, says Ira Wallace at Southern Exposure Seed Exchange.

Blackeye peas and other crowder peas:

The tips and leaves are edible. Garden Betty writes about many of these less usual greens, from a salad perspective, in Summer-Lovin’ Salad Greens