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

Bare Root Transplants

Lettuce seed bed, with Muir, Jericho, Sierra lettuces. Photo Bridget Aleshire
Lettuce seed bed, with Muir, Jericho, Sierra lettuces.
Photo Bridget Aleshire

Last week when writing about Lettuce Varieties for January I mentioned how we grow all our outdoor lettuce as bare root transplants. From January through to the end of April, we sow lettuce seed in open flats. After that date, we sow in outdoor nursery seed beds, and simply dig up the transplants when big enough and replant them in our raised beds. We transplant 120 lettuce outdoors each week until early October and then transplant in our greenhouse and our hoophouse. We also grow many other crops (all the easy to transplant ones) in open flats, or in nursery seed beds.

This method has gone “out of fashion”, but perhaps it will come back in! Atina Diffley (Author of Turn Here Sweet Corn and Wholesale Success) has written a blog post about bare-root brassica transplants at atinadiffley.com/blog/. She has written a thorough-and-concise 9 page manual Seed Beds: Bare Root Field-grown Brassica Transplant Production.  It includes a chart of pros and cons of bare-root transplants compared to container-grown greenhouse transplants.

Using bare-root transplants does require a bit more attention to technique than popping plugs into the ground. But it’s not that difficult and we train new people every year with success.

Why bare-root transplants?

Bare-root transplants save a lot of time and money, compared to growing in flats. They also save on valuable greenhouse space. The plants get very sturdy, because they have the full depth of soil in which to develop big roots. Starts grown in outdoor seedbeds are already acclimated to cooler conditions than plants in your greenhouse. They are less prone to drying out than seedlings in flats, but do be ready to protect them from bugs.

Which crops work best?

Bare-root transplants can suffer more transplant shock than plugs, so start with “easy to transplant” crops, such as brassicas (cabbage, kale, collards, broccoli, Brussels sprouts, kohlrabi), lettuce, onions and leeks. Tomatoes and peppers are worth trying next. See the Chart “Relative Ease of Transplanting Bare-Root Vegetable Seedlings” free online in Knott’s Handbook for Vegetable Growers. Avoid trying bare-root cucurbits (squash, melons, cucumbers).

Bare-root transplants can be used on any scale, from backyard to large farm. See the impressive photos of huge beds of cabbage transplants in Atina Diffley’s manual. They can be used at various times of year, and from indoors to outdoors and vice-versa.

Spring bare-root transplants started in a hoophouse, planted outdoors.

For the earliest spring transplants, bare-root hoophouse starts are a nice option. For us, onion seedlings overwintered in the hoophouse have worked very well. Seedlings outdoors or in a cold-frame suffer too much winter-kill. We don’t want to fuss with flats in November-February. We’re in zone 7, at 38̊ N. We sow onions in the soil in the hoophouse November 10 and 20, with a backup sowing on December 5. We plant them outdoors as early in March as we can. The onions get to thin-pencil-size by March 1, which we couldn’t do from a spring sowing. Onion roots are tough and thick, not thread-like – they are easy as bare-root transplants.

We sow spinach, collards and kale in the hoophouse in mid-late January and plant them outdoors in early March. This is a lot less work than using flats, and our comparison trials with bare-root spinach showed results were just as good as spinach in Speedling plug flats. We have tried early lettuce transplanted from the hoophouse, but the plants were not as sturdy as those in flats.

Senposai, the Thousand Wonder Green, Credit Kathryn Simmons
Senposai, the Thousand Wonder Green,
Credit Kathryn Simmons

Outdoor bare-root transplants

See my book Sustainable Market Farming, for more details of growing outdoor bare root transplants. We grow lettuce this way from April to September, and fall brassicas in June and July, in one of our permanent raised beds where the soil is friable and free-draining. Also see Atina Diffley’s manual for cultivation tips.

We grow outdoor cabbage, broccoli, collard, senposai and Yukina Savoy transplants in seedbeds for 3-4 weeks in June and July, covered with ProtekNet on hoops. We transplant in July and early August for harvest in October and November. We prefer this to direct sowing, because it is much easier to keep the relatively small seedbed watered and bug-free. For large amounts use an EarthWay seeder. Atina Diffley recommends the leek seed plate for brassicas.

Outdoors to indoors

In September we make an outdoor seedbed for crops to transplant into our hoophouse in October. The late summer hoophouse crops get a few extra weeks to finish up. Because the hoophouse can be warmer than ideal for lettuce germination until well into fall, it often works better to start plants in a cooler location, then move the plants. In September in our climate, four-week old lettuce plants will be a good size.

As well as ten varieties of lettuce, we sow various Asian greens and Brite Lites chard. Nine days later we sow another ten varieties of lettuce, white and red Russian kales, senposai and frilly mustards such as Ruby Streaks, Red Rain, Golden Frills, Scarlet Frills as well as green mizuna. We cover the seedbeds with hoops and ProtekNet and water daily. Transplanting these plants starts October 1 with the fast-growing pak choy, Chinese cabbage and Tokyo Bekana. The other transplants follow, as they reach the right size.

Brassica seedbed protected from insects with ProtekNet and hoops. Photo Bridget Alsehsire
Brassica seedbed protected from insects with ProtekNet and hoops.
Photo Bridget Alsehsire

Stay indoors in winter

In October in the hoophouse we sow short rows of “brassica fillers”, mostly senposai, Tokyo Bekana and Maruba Santoh. These grow fastest, which becomes more important in the dark winter days. We fill gaps in any brassica bed, that occur either because of disease, or of harvesting. In late October and early November we sow filler leaf lettuce varieties and filler spinach. These extra plants help us out if something goes wrong, and give us the chance to grow some extra crops after the first ones have been harvested.

How much to sow

Our formula for sowing seedbeds in the hoophouse is to divide the final row length of brassica plants by 10 to give the minimum length of seed row to sow. These plants will be transplanted 10″-12″ (25-30 cm) apart. For onions (to be transplanted 4″ (10 cm) apart), we divide the number of plants wanted by 20 to give the row feet (67/m), but we sow this amount twice, about 10 days apart. Outdoors for the fall brassicas, we sow around a foot (30 cm) of seed row for every 12′-15′ (3.6-4.6 m) of crop row, aiming for 3-4 seeds per inch (0.75 cm apart). These plants will be transplanted 18″ (46 cm) apart. It’s important to weed and thin the seedlings to 1″ (2.5 cm) apart soon after they emerge.

Transplant age and size

There is quite a lot of flexibility about when a start can be transplanted, but there are accepted ideals to be aimed for. The University of Florida Vegetable Horticulture Program Vegetable Transplant Production page  has a wealth of transplant information. Transplants grown over winter or in very early spring in a hoophouse will take longer to reach plantable size than those sown in spring or summer.

Suitable conditions for transplanting

The ideal conditions for outdoor transplanting are mild windless afternoons and evenings just before light steady rain. Transplanting late in the day gives the plant the chance to recover during the cooler night hours when transpiration is slower. Shadecloth or rowcover can reduce the drying effects of wind and sun. Damp soil is important before, during and after transplanting.

Bare-root transplanting technique

When you dig up your bare-root transplants, leave some soil clinging to the roots, to help the plants re-establish quicker. They don’t need a full handful of soil for each plant. Just dig up a clump and give it a light shake, to leave the majority of the soil behind, and some still on the roots. This means less damage to the root hairs. Be sure to dig deep enough so you don’t damage the tap roots. Water your plants the day before and an hour before lifting (pulling) them. In hot weather, keep the plants as shaded as possible while transplanting.If necessary water the soil ahead of planting.

We use plastic dish-pans to carry our plants from seedbed to field, and I tell people to only dig up what they think they can transplant in half an hour, so that plants don’t sit around for too long. Push the trowel into the soil, using the dominant hand, push it forwards, shake a plant loose from the clumps in the dish-pan with the other hand, and slip a plant in behind the trowel. Pull out the trowel, keeping it in your hand while you close the soil against the stem with your planting hand and the trowel. (Efficient workers keep a hand on the trowel at all times, never setting it down.) Move to the next spot and repeat. When setting out a large number of plants, water every 20-30 minutes if you don’t have drip irrigation running (a bit less often if you do) regardless of the number of plants set out. If the person is skilled and moving fast, and the weather is not outrageously hot or windy, I might let an hour go by before pausing to water. The advantage of getting a lot of plants in the ground proficiently and quickly might outweigh the need to water more often, as the plants are not having their roots exposed to the air for as long when they are planted fast. The hand-watering really helps the soil settle around the roots, and after that the damp soil can wick moisture from the irrigation towards the plant.

Aftercare: water, rowcover, shadecloth

Water your plants the day after transplanting, on days 3, 7 and 10, and then weekly, if it doesn’t rain when you’d like it to. Shadecloth draped over recently transplanted crops can help them recover sooner from the shock in hot sunny weather. We use 50% shade, in 6′ (1.8 m) width, with wire hoops to hold the shadecloth above the plants. This improves the airflow as well as reducing the abrasion or pressure damage done to the plants. The airflow through shadecloth is better than with floating rowcovers. ProtekNet allows good airflow too, and keeps bugs off.

Shade cloth on lettuce seed bed. Photo Nina Gentle
Shade cloth on lettuce seed bed.
Photo Nina Gentle

 

 

 

Twin Oaks Garden Task List for February

Greenhouse interior with early spring seedling flats.Photo Kathryn Simmons
Greenhouse interior with spring seedling flats.
Photo Kathryn Simmons

PlanningWeek 1:  Revise Crop Planting Quantities chart, Perennials worksheet, Harvest and Food Processing Calendars, Veg Finder, and Phenology Chart. Week 2:  Revise Fall Brassicas Spreadsheet, Onion Plan and Log, Sweet Potato Plan. Revise and post Paracrew Invitation. Week 3: Write Seed Saving Letter. Revise Blueberry Map and Log, Grape Map and Log. Week 4: Revise Crop Planting Specs sheet, revise Garden Planning Calendar, File notes, prune files.

Lettuce Factory: Sow lettuce #3, 4 in flats (short-day fast varieties, every 14 days).

Spread compost & till beds for spinach, beets, favas, lettuce, onions, little alliums, turnips, senposai, kohlrabi, cabbage, kale, collards when soil dry enough.  Till beds for carrots 1-3, with or without compost.

#1 Spring Tractor Work  – Compost and disk areas for broccoli and potatoes when dry enough, or till.

Early Feb: in greenhouse sow: cabbage, collards, senposai, kale, kohlrabi, broccoli #1, celery, celeriac

Sow spinach outdoors if Jan sowings fail: 4oz/bed pre-sprouted. Transplant spinach from hoophouse [or flats].

Sow fava beans (seed is in peas bucket). Plant small potato onions if not done in January.

Mid-month: in greenhouse: Sow lettuce #3, and resow hoophouse peppers as needed. Spot cabbage, lettuce#3, hoophouse peppers, kale, collards, and harden off.

February pepper seedlings in the greenhousePhoto Kathryn Simmons
February pepper seedlings in the greenhouse
Photo Kathryn Simmons

Sow carrots #1 outdoors with indicator beets. Flameweed. Finish planting spinach, (direct sow if not enough transplants).

Buy seed potatoes mid-month and set out to greensprout (chit) before planting: 65°F (19°C) and light.

[Strawberries: plant new bought plants, if applicable.]

Late Feb, sow carrots # 2 (flameweed);

Really finish transplanting spinach. If needed, presprout 4oz/bed spinach for 1 week before sowing.

Till and sow areas for clover cover crops (eg grapes, eggplant beds), or oats, from 2/15.                    

Transplant fall-sown onions ½-3/4” deep, when no thicker than pencils. Weed over-wintered spinach, kale, collards.

In greenhouse sow broccoli #2 (2 weeks after 2nd), (shallots), lettuce #4, hoophouse cukes.

Perennials: Finish weeding. Give compost, if not done in fall, including strawberries and grapes.  See list for January.  Transplant bushes, canes, crowns if needed. Mulch. Finish pruning blueberries, ribes. Prune grapes before 3/21 – see last year’s log notes about replacement limbs needed, etc. Summer raspberries: cut out old canes. Install irrigation. Prepare sites for new grapevines, if needed.

Vates kale over-wintered Photo Twin Oaks Community
Vates kale over-wintered
Photo Twin Oaks Community

Harvest: (Chard?), collards, kale, spinach, leeks.