Time to Sow More Fall Brassica Crops

 

Young tatsoi plants.
Photo Bridget Aleshire

See my recent post for info about fall broccoli and cabbage. Here I provide some more information and discuss other brassicas you could grow in the fall.

Temperature and Timing for Fall Brassicas

  1. Germination: Brassica seeds will germinate at soil temperatures from 41°F (5°C) to 95°F (35°C). 41°F (5°C) can take 45 days for some brassicas, but in summer and fall, this isn’t the end of the thermometer we worry about! In summer and fall, soil temperatures are enough to germinate brassicas in 3-10 days. Optimum soil temperatures for germination are
  • 77°F (25°C) for most Asian greens, broccoli, Brussels sprouts, cauliflower, collards, kohlrabi, pak choy;
  • 86°F (30°C) for cabbage, including Napa cabbage, kale, turnips and rutabagas;
  • 68°F (20°C) for mustard greens, and perhaps arugula (which might do better even cooler)
Vates kale seedlings for bare-root transplanting outdoors.
Photo Pam Dawling
  1. Cold-Hardiness: Consult this list of winter kill (air) temperatures for brassicas, for the crops you are growing.
  • 32°F (0°C):  some cauliflower curds, some pak choy
  • 27°F (-3°C): many cabbage varieties
  • 22°F (-6°C): some varieties of arugula
  • 20°F (-7°C): broccoli heads (maybe OK to 15°F (-9.5°C)), some Brussels sprouts, some cabbages (the insides may still be good even if the outer leaves are damaged), some cauliflower varieties, some collards (Georgia Cabbage Collards, variegated collards), some mustards/Asian greens (Tendergreen), radishes (Cherry Belle), most turnips (Noir d’Hiver is the most cold-tolerant variety).
  • 15°F (-9.5°C): some broccoli and cauliflower leaves, some cabbage (Kaitlin, Tribute), Red Russian and White Russian kales, kohlrabi, rutabagas (American Purple Top Yellow, Laurentian), most covered turnips, winter cress.
  • 12°F (-11°C): some broccoli perhaps, some Brussels sprouts, some cabbage (January King, Savoy types), most collards, Koji greens, covered rutabagas
  • 10°F (-12°C): Purple Sprouting broccoli for spring harvest, a few cabbages (Deadon), some collards (Morris Heading can survive at least one night), Belle Isle upland cress, probably Komatsuna, Chinese Thick-Stem Mustard may survive down to 6°F (-14°C), covered winter radish (Daikon, China Rose, Shunkyo Semi-Long survive), Senposai leaves (the core of the plant may survive 8°F/-13°C), Tatsoi, Yukina Savoy.
  • 5°F (-15°C): some kale (Winterbor, Westland Winter), many of the Even’ Star Ice Bred greens varieties and the Ice-Bred White Egg turnip are hardy down to 6°F (-14°C)
  • 0°F (-18°C): some collards (Blue Max, Winner, McCormack’s Green Glaze), Even’ Star Ice-Bred Smooth Leaf kale
  • -5°F (-19°C): Leaves of overwintering varieties of cauliflower, Vates kale survives although some leaves may be too damaged to use. Lacinato Rainbow Mix kale may survive this temperature.
Frosty daikon leaves.
Photo Bridget Aleshire
  1. Your Climate: Consult WeatherSpark. com to see when it begins to get too cold in your area. At our farm, the average daily low temperature on November 30 is 36°F (2°C). Decide your ideal harvest date for each crop. Although kohlrabi can take 15°F (-9.5°C), I’d want to get it all harvested by November 30.
  2. Days to Maturity: Next factor in the number of days a crop takes to reach maturity. Work back from your desired harvest date, subtracting the number of days from sowing to maturity (or from sowing to transplant, plus from transplant to maturity). Work back another two weeks for the slowing rate of growth in fall. And perhaps work back another two weeks in case in gets colder earlier than usual. This provides your sowing date.
  3. Mid-Winter Harvests: For crops that survive your winter, are you sowing to harvest in the fall, during the winter, or only in early spring? Brassicas for early spring harvest only can be sown in September or October in our climate. For those to be harvested during the winter, you need to have big enough plants going into the winter, to provide sustainable harvests (once a week in November and February and more in spring, plus maybe once a month in December and January)
Overwintered Vates kale.
Photo credit Twin Oaks Community

Various Fall Brassica Crops

In the summer we try to have a No Visible Brassicas Month to break the lifecycle of the harlequin bugs. Once our spring kale is finished, the spring cabbage gathered in, and the spring broccoli mowed down, the only brassicas are seedlings hidden under insect netting. Our hope is to starve out the harlequin bugs or at least deter them from making too many more.

We sow other fall outdoor brassicas a bit later than cabbage and broccoli. These get transplanted from our netting-covered nursery seedbeds, to our raised bed area which is more accessible for winter harvesting and more suited to small quantities.

Asian Greens

Outdoors we grow Senposai, Napa Chinese cabbage and Yukina Savoy. We have also sometimes grown tatsoi and komatsuna. Note that senposai grows quite large – give it similar spacing to collards.

We sow Asian greens for outdoors in the last week of June and first week of July, aiming to eat them before we start harvesting the ones in the hoophouse, which feed us all winter. We use Asian greens outdoors as quick-growing greens to fill the gap before our main fall greens (spinach, kale, collards, cabbage, broccoli) are ready to harvest. We don’t grow a lot outdoors.

If you don’t have a hoophouse, you can sow for outdoors later into the fall than we do, to get a longer harvest season than you otherwise would. And you certainly can direct seed them.

Yukina Savoy outdoors in December, after several nights at 16-17°F (-8 to -9°C)
Photo Kathryn Simmons

Collards

We sow collards in the first two weeks of July and transplant the bare-root transplants from the nursery bed when they are 3-4 weeks old. We plant at 18” (46 cm) in the row, with rows 12” (30 cm) apart. (if you grow a large kale, you might want similar spacing. Our Vates kale is small)

Morris Heading collards.
Photo Kathryn Simmons

Brussels sprouts

are rather a challenge in our climate, and not worthwhile. We have worked on finding the best variety (Oliver) and timing for our situation. Harvest timing is critical, as Brussels sprouts will not overwinter here.

Cauliflowers

are a tricky crop for us too. Be sure to check the “days to harvest” for each variety (they vary widely) and sow at a realistic date to get a crop before too many frosts endanger the curds. The number of days quoted for fall varieties of cauliflower already allows for the expected rate of growth at that time of year, so the 14 days for slower growth isn’t a factor. However, cauliflower is more tender, so allow for the possibility of a fall frost earlier than average.

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

Kohlrabi

We sow Vienna kohlrabi mid-July and transplant early August at 8” (20 cm) apart in the row, with 9-10” (23-25 cm) between rows. Later sowings (up till early September) would also work for the fast maturing varieties. Superschmelz Kohlrabi (60 days from transplanting) can also be summer sown for fall harvest. It produces 8-10” (20-25 cm) bulbs, which remain tender and an attractive globe shape.

Kale

We direct-sow two neighboring beds of kale on each of 8/4, 8/10, 8/16 and then carefully thin them, leaving one plant every 12” (30 cm). These plants grow quicker than transplants, as they have no transplant shock. Meanwhile, if we have gaps, we use the carefully dug thinnings from those beds to fill them. We want a lot of kale, and there isn’t time to transplant it all. Dividing up the sowings lets us focus on watering just one pair of beds at a time. 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).

An outdoor bed of young Vates kale Photo Kathryn Simmons

Rooty Brassicas

Radishes, rutabagas and turnips are also brassicas, but I won’t say more here. look in the further resources.

Brassica Aftercare

Brassicas started in hot conditions do not usually bolt if they have enough water.

 

Brassica seedlings under ProtekNet in August.
Photo Pam Dawling
  • Protect seedlings and the new transplants with insect netting if you have brassica leaf pests (most of do!) You can remove the netting when the transplants are well established, or leave it on.
  • Use shadecloth to keep greens cool in hot weather, or plant them in the shade of other plants.
  • To keep crops in good condition later into the winter, use rowcover. I recommend thick Typar 1.25oz rowcover, which provides 6F degrees of cold protection. I wouldn’t spend the money on anything thinner, it’s too frustrating! We do not normally use rowcover in the winter for kale and collards, as they will survive without. In harsh winters we lose the collards.

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

Further Fall Brassica Information

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

Fall broccoli patch.
Photo Kati Falger

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.

Vates kale.
Photo Nina Gentle

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.

Young beets.
Photo Pam Dawling

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