Producing Asian Greens©Pam Dawling 2015

Twin Oaks Community, Central Virginia

Author of Sustainable Market FarmingPublished by New Society Publishers

SustainableMarketFarming.com

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Outline1. Meet the Asian Greens

2. Crops I recommend

3. Crops that might work for you (not for us)

4. Crop requirements

5. Dealing with pests and diseases

6. Growing in spring

7. Growing outdoors in fall

8. Growing in the winter hoophouse

9. Harvesting

10. Minimizing nitrate accumulation in winter

11. Seed saving• Pak Choy. Credit Ethan Hirsh

1. Meet the Asian Greens!

• Huge range of attractive varieties

• Quick-growing, bring fast returns

• Grow when you normally grow cabbage or kale

• Short spring season, bolt when it gets hot

• Long fall season, no bolting. Success depends on getting them germinated and planted in June and July

• Grow all winter in hoophouses in our area.

• Let’s look at the advantages.

Blues Napa Chinese cabbage shown hereCredit Ethan Hirsh

Advantages A quick way to fill out your

market booth or CSA bags A catch crop for spaces where

other crops have failed or otherwise finished early. Keep a flat of seedlings ready, pop plugs into empty spaces as they occur.

Better able to germinate in hot weather than lettuce.

Faster growing than lettuce Some of the faster-growing types

are ready for transplanting 2 weeks after sowing (or you can direct sow them)

Trial many kinds, use unwanted seed in baby salad mix!

Photo credit Ethan Hirsh

Healthful Diversity! Flavors vary from mild to

peppery - read catalog descriptions before growing lots

Colors cover the spectrum: chartreuse, bright green, dark green and purple.

Nutritious as well as tasty. High in carotenoids, vitamins A

and C, calcium, iron, magnesium and fiber.

Help prevent high blood pressure, heart disease and stroke.

Also contain antioxidants which fight against cancer and protect eyes from macular degeneration

Photo Credit Ethan Hirsh

Who’s Who – Three main groups

1) The turnip family, Brassica rapa, of Asian origin

a. Some crops are Brassica rapa var. pekinensis (napacabbage, michihili, celery cabbage);

b. others are B. rapa var. chinensis (bok choy)

c. B. rapa var. japonica (mizuna).

d. B. rapa var. narinosa (tatsoi)

e. B. rapa var. perviridis(komatsuna)

Different sources use different names.

2) The cabbage family, B. oleracea, of European origin

Kai-lan, Chinese kale

3) The Chinese Mustard family, B. juncea

Ruby Streaks (shown here, Credit Johnnys Seeds),

Golden Frills, Red Rain

2. Crops I recommend1a. Brassica rapa var. pekinensis

Pe tsai, or pei tsai, two types:Wong Bok

• Napa cabbage is a Che-footype of wong bok,

• Cylindrical cabbages such as Michihili (below) and Jade Pagoda are Chihili types of wong bok

• Photo credit Southern Exposure Seed Exchange

Non-Wong Bok• Celery cabbage types: loose-

leaf, non-heading, fast-growing vegetables with light green leaves and white petioles. Maruba Santoh and Tokyo Bekana (below)

• Photo Credit Johnnys Seeds.

1a. Brassica rapa var. pekinensis.

Napa cabbage • A type of wong bok• We like Blues (52 days from

seed to harvest) best • Kasumi has the best bolt

tolerance and is larger: 5 lb(2.3 kg) compared to 4 lb(1.8 kg)

• Orange Queen is a colorful but slower-growing variety (80 days)

• All are hardy to about 25°F (–4°C)

• Stores better than michihilitypes.

1a. Brassica rapa var. pekinensis

Michihili/Cylindrical Wong Bok Chinese cabbage

• Produces 16" (40-cm) tall heads 6" (15 cm) across.

• Very tender, light green leaves• Excellent for stir-fries and

pickling. • More stress tolerant and

resistant to bolting and black speck than Napa cabbage,

• Cannot be stored as long.• We like Jade Pagoda (72 days)

and the O-P Michihili (72 days)Photo credit Southern Exposure Seed

1a Brassica rapa var. pekinensis

Celery cabbage pe tsaiPhoto credit Johnnys Seeds The second type of B. rapa:

• a fast-growing, looseleaf, non-heading vegetable with light green leaves and white petioles.

• Can be ready for harvest in 3–4 weeks after sowing.

• More heat tolerant than Napa. Cold tolerant to 25°F (-4°C)

• Tokyo bekana, MarubaSantoh

1a Brassica rapa var. pekinensis

Maruba Santoh

• A fast-growing chartreuse (yellow-green) tender-leafed plant

• Can be harvested as baby leaves

• Or the leaves and wide white stems of the mature plant provide crunch for salads

• Only 21 days to baby leaf, 35 days to maturity, and is fairly bolt resistant

• Photo credit Ethan Hirsh

1a or b Brassica rapa var. pekinensis or var. chinensis (opinions vary)

Tokyo Bekana• Fast-growing tender

chartreuse frilly, leafy plant. • 21 days to baby crop, 45

days to full maturity• Can be used for salad

leaves during late-summer lettuce shortages.

• Mild flavor - many people don’t even notice they are not eating lettuce!

Young seedlings in November hoophouse shown here.

Credit Ethan Hirsh

1b. Brassica rapa var. chinensis

Pak choy/bok choi

• Previously known as Chinese mustard cabbage

• Sturdy white leaf stems, big green leaves. Usually harvested as a head 12"–15" (30–38 cm) tall

• 45–55 days to maturity

• All are hardy down to 32°F (0°C), most varieties to 25°F (-4°C)

• Photo credit Johnnys Seeds

Pak choy

• Can be picked as individual leaves, for bunches of mixed braising greens or stir-fry combinations

• We grow Prize Choy or Joy Choi

• There is also red choi (a 45-day, red-veined baby leaf or maroon-leaved full-size version)

• Photo credit Ethan Hirsh

1c. Brassica rapa var. japonica

Mizuna/kyona• Very easy to grow,

tolerates cold wet soil

• Use for baby salads after only 21 days

• or thin to 8"–12" (20–30 cm) apart, to grow to maturity in 40 days

• Fairly heat tolerant (well, warm tolerant)

• Cold tolerant to 25°F (-4°C)

Photo credit Ethan Hirsh

Mizuna

• Mild flavor• Regrows vigorously

after cutting • Ferny leaves - add color

and loft in salad mixes• Available in green or

purple (but Ruby Streaks is much better then Purple Mizuna!)

Mizuna with some purple Ruby Streaks and some strap-leaved mibuna and purple mizuna mixed in.Photo credit Ethan Hirsh

1d. Brassica rapa var. narinosa

Tatsoi/tah tsoi

• A small plant, a flat rosette of shiny, dark green spoon-shaped leaves and green-white stems

• 21 days for baby salads; 45 days for cooking

• Mild flavor, an attractive appearance

• Very cold tolerant, hardy to 10°F (–12°C)

• Easy to grow - here’s how -

Tat soi

• Direct sow and then thin into salad mixes, leaving some to mature at 10" (25 cm) across for cooking greens.

• Can transplant at 6" (15 cm)

• Kitazawa Seeds have a Red Violet tatsoi, with an upright habit

• Photo credit Wren Vile

1e. Brassica rapa var. perviridis orBrassica rapa var. komatsuna

Komatsuna

• Also known as mustard spinach (as Pak Choy is too!) and Summer Fest

• Green or red (purple)• Baby salad size in 21 days, full size in 35

days• Grows into a large plant 18" (45 cm) tall• Individual leaves can be picked and

bunched • Or the whole plant can be harvested • The flavor is much milder than the

English name suggests - mildly peppery • Cold-tolerant to 15°F (-9.5°C), perhaps

10°F (-12°C)

Photo credit Evergreen Seeds

1. Brassica rapa or 3. juncea

Yukina Savoy

• like a bigger tatsoi,

• blistered dark green leaves and stems

• delicious flavor

• about 12“ (30 cm) tall

• Tolerant to heat and cold – down to 10°F (-12°C)

• Transplant at 12" (30 cm)

• 21 days to reach baby size, 45 days to full size

Yukina SavoyOutdoors in December, after several nights at

16-17°F (-8 to -9°C)

1e. Brassica rapa var perviridis& 2. Brassica oleracea

Senposai - Our star of Asian greens • A cross between

komatsuna and regular cabbage.

• A big plant producing large, round, mid-green leaves which are usually harvested leaf by leaf.

• Delicious sweet cabbageyflavor, tender texture.

• Photo credit Kathryn Simmons

Senposai• Transplant at 12"–18"

(30–45 cm) spacing; it really will use all this space

• Very productive, grows fast. Only 40 days to mature.

• Heat and cold tolerant (down to 12°F (-11°C)

• Cooks quickly (much quicker than collards)

A bed of senposai 15” apart in the row, 3 rows in 48” Credit Kathryn Simmons

Senposai in November the young hoophouse crop is almost ready to take over from the well-used outdoor crop.

3. Brassica juncea

Ruby Streaks – another starRuby Streaks with MizunaCredit Ethan Hirsh

Ruby Streaks Credit Southern Exposure Seed Exchange

Other B. juncea mustards:

Golden Frills, Scarlet Frills, Red Rain

Johnny’s Red Splendor Golden Frills

Asian-type brassica salad mixesWild Garden Pungent Mix, Brassica juncea, (Wild Garden Seeds, Fedco).

A cross of pungent Indian mustards for those who like Big Flavor. 40 days to harvest.Photo credits Wild Garden Seeds

Pink Petiole Mix, Brassica rapa (Wild Garden Seeds, Fedco).

Fast-growing, cold tolerant, adds a touch of color to the brassica portion of winter salad mixes. A varied mix of colors and shapes. Ready in 40 days.

Pseudo-Asian GreensPink Lettucy Mustard, Brassica rapa japonica, Mild-flavored at all growth stages.Photo credit Wild Garden Seeds

Ornamental and garnish kales and cabbages add color and texture. We like Nagoya Red and White and Red ChidoriPhoto credit Evergreen Seeds

3. Crops that might work for you (not for us)

Too small and/or too short-lived Hon Tsai Tai, Brassica rapa, (like a purple broccoli raab). Also

known as Choy Sum. Mostly stem with small clusters of buds. In climates cooler than Zone 7 this might be productive in the fall. For spring it could be a challenge most places. It matures in only 35–40 days. Hardy to 23°F (–5°C). Photo credit Johnnys Seeds

Broccoli Raab, Brassica rapa ruvo. We had the same trouble with this as with Hon Tsai Tai

Mei Qing Choi, Brassica rapa var. chinensis. A miniature 6" (15 cm) pak choy. We don’t do well with miniature crops. These might suit your market, but we do better with larger vegetables. It matures in less than 45 days, a definite plus

Vitamin Green/Bitamin-Na/Yokatta-Na, Brassica rapa var. Narinosa. A slender, white-stemmed plant, about 12" (30 cm) tall. It can be planted 4" (10 cm) apart, or direct sown and thinned. Tolerates heat and cold. Quick-growing with good flavor, not pungent: 21 days for salad mix, 45 to its full size

More non-starsThese were too big and gnarly for us.

Tyfon Holland Greens - a strong plant, a hybrid of komatsuna with a heading brassica. Could be good in a survival situation, or to grow for goats. Not a gourmet green. Hardy down to 20°F (-7°C).

Tenderleaf – a big, sturdy, OP plant. Quick-cooking, mild-flavored, despite appearances. Selected from a cross of Tendergreen and tatsoi.Very disease-resistant and cold tolerant down to 20°F (-7°C). Can be sown later in the fall than other greens - could be the solution if your original plan didn’t work. Can be a useful salad mix crop at the baby stage. We let ours get too big.

Mizspoona, Brassica rapa, a large sturdy plant, 40 days to maturity. A sweet flavor with a good balance of mild zinginess. A gene pool (variable plants). Mizuna crossed with Tatsoi.Credit Wild Garden Seeds

Other Big Greens • Chinese Thick-Stem Mustard (SESE, Fedco, Even' Star Organic Farm, Maryland). Multiple cuttings of balanced-flavor salad mix crop to fill the CSA bags. Extremely cold tolerant.

• Toraziroh, Brassica oleraceaalgoblabria, a robust producer of high yields of large leaves with a good, not overpowering flavor. Related to Chinese kale or Chinese broccoli. Relatively slow to bolt, ready in 45 days

• Transplants of Red Giant Mustard

Photo credit Southern Exposure Seed Exchange

• Mature Red Giant Mustard

Photo credit Evergreen Seeds

Mustard greensMustards such as Red Giant, Osaka Purple, Brassica juncea, and American

Mustards (eg Southern Green Wave) are too hot for us, even at 3" (8 cm) leaves. Hardy to light frosts. Attractive colors. 21 days to baby leaves, 40–45 days to full

size

Asian non-brassica greens

Chrysanthemum greens/shungiku, Chrysanthemum coronarium. These have a very distinctive aromatic flavor, which you may ormay not love.

The flowers are very pretty, if you give up harvesting the plants.

21 days for baby greens, 45 days to full size.

Photo credit Evergreen Seeds

4. Crop requirements for Asian greensSimilar care requirements to other brassicas,

Shallow rooted - Pay extra attention to providing enough water during hot weather to prevent bitter flavors and excess pungency,

Do close monitoring of pests, which can build up large populations during the summer.

Very fertile soils grow the best Asian greens,

Turn in leguminous cover crops

or compost to

provide adequate nutrition.

Sow or Transplant?

We almost always transplant brassicas because we use our growing spaces very intensively.

Transplanting gives the previous crop extra time.

If we have 4 weeks between the end of one crop and transplants going in, we sow buckwheat to add organic matter and smother weeds.

We usually choose this cover crop opportunity rather than direct sow greens.

We grow a lot of brassicas and our crop rotation is always pushed and stretched by the amount of brassicas we’d like to plant – transplanting allows the soil extra weeks without brassicas.

Transplanting for fall crops In summer, the faster growing

types are ready to plant out 2 weeks after sowing. Napa cabbage, Tokyo Bekana and Maruba Santoh are in this category.

Most others transplant best at 3–4 weeks of age (less time than needed in spring). We transplant outdoors July 10 - July 31.

To minimize transplant shock, water the plants well an hour before transplanting, get them in the ground as quickly as possible and water again.

Shadecloth or rowcover will help keep the breezes (if any!) and strong sun off the plants.

Irrigation Shallow-rooted, need plenty of

water to grow pleasant-tasting leaves.

1” (2.5 cm) of water per week is often enough

During very hot weather, 2” (5 cm) is better

Drip irrigation saves water and reduces disease and weed pressure.

Overhead irrigation can be cheaper and easier to set up for crops that will be harvested before much time has passed.

Overhead sprinklers can wash off aphids - could be all the control you need

5. Dealing with pests and diseases

ProtekNet on hoops Mesh fabric with small holes is

better than rowcover in hot weather - airflow is better and it heats less.

ProtekNet Pest Control Netting is made of clear high-density polyethylene with UV resistance and a lifespan of eight to ten years. Its light transmission is 90 percent. It is available from Purple Mountain Organics in Maryland. The 1.35 ×1.35 mm 60 gm/m2 mesh is one-sixth the length of a cucumber beetle. It also protects crops against weather damage.

Pests : flea beetles Brassica flea beetles are a different

species from the ones that plague eggplant, and they can only fly a few hundred yards (meters).

If we get flea beetles, we use Spinosad, an enzyme produced by a soil organism.

Garlic spray, Miller’s Hot Sauce, kaolin and white sticky traps have been suggested.

You can also catch them with a vacuum cleaner, or inside a bucket coated with Tanglefoot paste (hold the inverted bucket over the plant, shake it and catch the jumping beetles in the goo).

Hb nematodes will also control them, as will neem oil or the braconid wasp Microtconus vittatoe Muesebeck.

ProtekNet – get smallest mesh

More Pests

Harlequin bugs are our worst brassica pests. We usually pick and kill them.

Aphids are worse in cooler weather (early spring), before their predators have arrived in high enough numbers. Insecticidal soaps can be used.

Caterpillars can be kept off the plants with rowcover or ProtekNet. Bt (Bacillus thuringiensis) will kill caterpillars if rowcovers fail. Bt degrades rapidly in sunlight so is best applied early evening or early morning, whichever seems likely to catch most caterpillars. The beneficial fungus Beauvaria bassianainfects caterpillars, but can get costly. Caterpillars have many natural enemies. In our garden the paper wasps eat caterpillars, and we also have the parasite Cotesia glomerata

Even More Pests

I used to think slugs were an endangered species in Virginia. When we put up our hoophouse, I found we were farming them! Slugs can best be caught at night with a flashlight. (Well, actually with scissors, by flashlight!)

Grasshoppers - We are trying to determine when the young hatch in July, so we know when we need to be most attentive to keeping them off our plants.

Vegetable weevil larvae have caused trouble In our hoophouse in January. They come out of the soil at night and make holes in the leaves. We have used Spinosadagainst them with some success.

Diseases Most of these greens are fast-turnaround crops, so if

some get sick, pull them out and move on in life.

If it’s fall you can probably sow some spinach to

provide greens without antagonizing the brassica

disease gods.

Clubroot is perhaps the longest lasting disease, requiring land to be taken out of brassica production for ten years.

Other diseases include various molds and wilts.

See ATTRA’s Cole Crops and Other Brassicas: Organic Production

6. Growing in SpringIn spring we sow in flats in

a greenhouse, to get an early start.

We transplant spring Asian greens at 4–5 weeks of age, about a month before our last frost date, and use rowcover for a few weeks.

Direct sowing has the advantage that thinningscan be used for salads.

Photo credit Kathryn Simmons

7. In Summer (for Fall Outdoor Crops)

We prefer outdoor seedbeds for summer sowings, because it is easier to keep the plants watered.

We make an outdoor nursery bed, sow at about three or four seeds per inch (5–10 mm apart), and cover with rowcover or ProtekNet.

The seedlings emerge in as little as three days in summer temperatures.

Bare-root transplants. Photo credit Ethan Hirsh

For Fall Outdoor Crops

We start sowing our fall Asian greens for outdoor planting around June 26 and repeat a week later for insurance (July 3), the same dates we sow fall broccoli and cabbage.

Last date for sowing these crops is about 3 months before the first fall frost date. In our case that means July 14–20.

Photo credit Kathryn Simmons

Season extension

Fast growing varieties can be succession sowed for a continuous supply.

Cold-hardy types can be harvested all winter in climates milder than zone 7.

Or they could be kept alive to revive in spring and provide earlier harvests than spring-sown crops.

Wild Garden Seeds and Even’ Star Farm specialize in producing seed for very cold-tolerant varieties.

Rowcovers on hoops will help keep these crops in marketable condition, and improve the microclimate, for better growth rate.

A well used bed of senposai in November. Credit Kathryn Simmons

Cold-Hardiness

• 32F (0C): Some Pak Choy

• 25F (-4C): Chinese Napa cabbage, MarubaSantoh, Mizuna, Tokyo Bekana, most Pak Choy

• 20F (-7C): Tendergreen, Tyfon Holland Greens

• 15F (-9.5C): perhaps Komatsuna

• 12F (-11C): Senposai

• 10F (-12C): Tatsoi, Yukina Savoy, probably Komatsuna

8. Growing in the winter hoophouseHoophouses are the place to be in winter, if you are an Asian green. Night-time protection of two layers of

plastic and an air gap – big difference!

September sowings thrive on sunny days and grow at a surprisingly fast rate.

When the daylight falls below ten hours, growth slows down till spring.

For most of the winter, our hoophouse plants are actively growing, not merely being stored for harvest (as happens in colder climate zones and outdoors), so we can continue sowing new hoophousecrops even in December.

Brassicas are the most productive crops in these conditions

• Photo credit Wren Vile

Persephone days and scheduling winter hoophouse crops

When the daylight is shorter than 10 hours a day not much growth happens. The dates depend on your latitude.

In Central Virginia, latitude 38° North, this period lasts two months, from November 21 to January 21.

The dates are modified by the time it takes to cool the soil and the air.

The effective dates for us are closer to December 15 -February 15.

To harvest in the darkest days of winter you’ll need to plan a good supply of mature crops to take you through. What has already grown before this period will provide most of your harvests.

Be aware of the increase in days to maturity in winter.

Fall outdoor sowings to transplant inside

• Sept 15: pak choy, Chinese cabbage, Yukina Savoy, Tokyo Bekana, Maruba Santoh, (chard, about ten varieties of hardy leaf lettuce and romaines)

• Sept 24: Senposai, more Yukina Savoy, mizuna (and arugula, Red and White Russian kales, another ten varieties of lettuce)

• We use hoops and ProtekNet, and water frequently.

Senposai. Credit Kathryn Simmons

Fall Hoophouse Planting - September Early September : We clear and

add compost to one of the beds and sow tatsoi (sprouted spinach seed,

radishes, scallions, Bulls Blood beets).

Sept 15 and Sept 24: We make outdoor sowings of crops to later transplant into the hoophouse at 2–4 weeks old.

At the end of September we clear summer crops from one more bed, add compost and work it in. We transplant Tokyo Bekana and Maruba Santoh at 2 weeks old, Chinese cabbage, pak choy and Yukina Savoy at 3 weeks.

Photo November hoophouse beds. Ethan Hirsh

Fall Hoophouse Planting - October Oct 15 we sow our first turnips. (around our first

frost date) for harvest from Dec 4. We like Red Round and Hakurei and have tried out Oasis and White Egg to find a cheaper replacement for Hakurei (Oasis is the closest).

Our neighbor Gary Scott sows Ace beets in 72 plug trays in mid Oct, transplants them in the hoophouse, harvests from mid-March.

Late October we sow more “filler” Asian greens, (and baby lettuce mix, our

second spinach, turnips and chard, and more radishes).

In the fourth week of October, we clear and prepare more beds and transplant the Senposai, mizuna, Yukina Savoy (and

the 2nd lettuce, kale, arugula) at 4 weeks old.

Early October, we sow some “filler” Asian greens, (and spinach,

more radishes and lettuce) to fill gaps later. We try hard to keep all the space occupied, mostly using Asian greens, lettuce and spinach. By mid-October we clear and prepare another bed and transplant lettuce at 10"

(25 cm) apart, and chard.Mizuna Photo credit Ethan Hirsh

Hoophouse Planting –November and December

Nov 10 we sow more mizuna, (turnips, arugula, more filler lettuce and spinach, and our first bulb onions for field transplanting as early as possible in the new year.

Nov 11-20 we sow tatsoi, (radishes, scallions,more bulb onion starts).

From Nov 10 on we aim to keep a fully planted hoophouse, and as each crop harvest winds down, we immediately replace that crop with another.

During December we use the “Filler” greens plants to replace casualties and heads of Chinese cabbage, Pak choy, Yukina Savoy each day as soon as we’ve harvested them. Pak Choy replacing Yukina Savoy here. Credit Ethan Hirsh

Hoophouse Planting –December to February

We stop filling gaps with Asian greens (and lettuces) on Jan 25, and fill all gaps after that with spinach transplants, until 2/20. After that we only fill gaps on edges of beds, leave centers free for tomatoes, etc.

After 2/20, we harvest the winter crops from the center rows first, plant the new early summer crops down the center, then harvest the outer rows bit by bit as the new crop needs the space or the light. This overlap allows the new crops to take over gradually.

Our winter and spring crops come to an end in March or early April

“Filler” transplants. Credit Ethan Hirsh

Daily hoophouse tasks in winter• Two hours work each day in winter in our 96’ x 30’ tunnel.

• Keep the temperature in the 65°F–80°F (18°C–27°C) range during the day, opening the big high windows, and the doors as needed. If the sun is shining we usually open the windows around 9 am and close them around 2:30 pm (a few hours before dark) to store some of the warmth.

• Even in cold weather, plants need fresh air! High-density cropping can really use up the carbon dioxide in a closed hoophouse very quickly. When this happens, photosynthesis crashes and plant growth becomes limited. Soil high in organic matter contains high levels of organisms that produce carbon dioxide. Dense plant canopies can trap this near soil level, where it is most useful.

• Our main task each day is harvesting. In the winter of 2009–2010, we had frozen soil or snow on the ground outside for a month (very unusual for us). Despite this we were able to keep a hundred people in fresh salad and cooking greens (with turnips and scallions for variety) for the whole month.

• Aside from harvesting, jobs include planting new crops, clearing old ones, spreading compost, hoeing, hand weeding and supplying water as needed.

• We have drip irrigation. In the middle of winter, not much water is needed, and we try to only water when a relatively mild night is forecast.

9. Winter Hoophouse Harvest Schedule• Harvest starts in November, with

mizuna, arugula, tatsoi and baby brassica mix along with beet greens, spinach, lettuce leaves for salad.

• From December we also have Tokyo Bekana, Maruba Santoh, as well as baby lettuce mix, chard, kale and turnips.

• The new year starts with YukinaSavoy and the bigger greens, including Senposai, pak choy, Chinese cabbage and kale feed us till mid-March.

Michihili cabbage Photo credit Southern Exposure Seed Exchange.

Harvesting Some of these greens are

harvested as whole heads; others can be harvested by the leaf and bunched or bagged.

The open rosette types, such as tatsoi or the bigger Yukina Savoy, are usually gathered closed and banded with plant ties or rubber bands.

Most can be grown for baby salad mix. With mizuna we do a “half buzz-cut,” snipping off leaves on one half of the plant an inch (25 mm) above the ground each time we come by.

• Tat soi shown here. Credit Ethan Hirsh

After Harvest

After harvest, get the crops into shade and a cooler as soon as you can. Some of the heading types can be stored in a walk-in cooler for quite a while, almost as long as regular cabbage. Pak Choy shown herePhoto Credit Ethan Hirsh

10. Minimizing nitrate accumulation in winter

In winter, when light levels are low, beware of high levels of nitrates in leafy greens.

A health hazard — nitrates can be converted in the body into nitrites, which reduce the blood’s capacity to carry oxygen and may be further converted into carcinogenic nitrosamines.

Nitrate accumulation

• Plants make nitrates during the night, and convert them into leaf material during the day. It takes about six hours of sunlight to use up a night’s worth of nitrates. In winter, a small handful of leafy vegetables can exceed the acceptable daily intake level of nitrate for an adult, unless special efforts have been made to reduce the levels.

• Spinach, mustard greens (Asian greens)and collardscontain about twice as much as lettuce; radishes, kale and beets often have two and a half times as much. Turnip greens are especially high, at 3 times lettuce levels.

To keep nitrate levels as low as possible: Grow varieties best suited for winter; Avoid fertilizing with blood meal or feather meal; use organic

compost. Ensure soil has sufficient P, K, Mg and Mo Water enough but not excessively; Provide fresh air as soon as temperatures reach 68°F (20°C), so that

carbon dioxide levels are high enough; Harvest after at least four (preferably six) hours of bright sunlight in

winter; Avoid harvesting on very overcast days; Avoid over-mature crops and discard the outer leaves. Harvest

crops a little under-mature, rather than over-mature; Use crops soon after harvest; Refrigerate immediately after harvest, store harvested greens at

temperatures close to freezing; Mix your salads; don’t just eat Asian greens!

11. Seed saving If you plan to grow seed of more than one brassica, carefully choose ones that

won’t cross. Be aware of the possibility of brassica crops being wrongly classified.

Also beware of brassica weeds.

For home use: at least 600 feet (200 m) isolation from other flowering brassicas.

For commercial seed: ¼ mile (400 m) with barriers or ½ mile (800 m) without.

Grow at least 120-300 plants in fall, pull out any atypical plants and leave the best over the winter. In the spring, let them bolt.

Why so many? Brassicas are outbreeding plants and, as such, are in danger of inbreeding depression (not enough genetic diversity), if too few plants are grown.

Save seed from at least 60 to 75 plants, and preferably 125 to 150.

As the seedpods dry, pull up the plants, and if your weather is damp hang them up to finish drying under cover. If you have high humidity, use a fan. Hanging plants inside paper sacks will reduce loss of seeds when the pods start to shatter.

You can stomp on the bags to shatter the pods, and then winnow and screen the seeds. See the Saving Our Seed Project guide listed in the Resources section.

Resources• Grow Your Own Chinese Vegetables, Geri Harrington, 1984, Garden Way

Publishing. Includes the names for these crops in different cultures.• Growing Unusual Vegetables, Simon Hickmott, 2006, Eco-Logic books, UK.• Oriental Vegetables: The Complete Guide for the Garden

and Kitchen, Joy Larkham, revised edition 2008, Kodansha, USA• Kitazawa and Evergreen Seeds have the most choices. • Evergreen’s helpful clickable list.

http://www.evergreenseeds.com/asveglis.html• Fedco Seeds and Johnny’s also have a good range.• Wild Garden Seed has many interesting home-bred varieties. Search under

Mustard. http://www.wildgardenseed.com• Even’ Star Farm Ice-bred Seeds http://www.localharvest.org/even-star-

organic-farm-M9994• Good Earth Seed Company (Tsang and Ma International)

P.O. Box 5644, Redwood City, California 94063. No English website.• ATTRA Cole Crops and Other Brassicas: Organic Production

https://attra.ncat.org/attra-pub/summaries/summary.php?pub=27• Saving Our Seed Project http://www.carolinafarmstewards.org/wp-

content/uploads/2012/05/BrassicaSeedProductionver1_1.pdf an excellent 24-page guide on organic brassica seed production

Producing Asian Greens©Pam Dawling 2015

Twin Oaks Community, Central Virginia

Author of Sustainable Market FarmingPublished by New Society Publishers

SustainableMarketFarming.com

facebook.com/SustainableMarketFarming