Chinese Cabbage and leafy greens, Brassica species
Last revised February 1, 2010
A great number of descriptive, ethnic and local terms contribute to confusion regarding Oriental greens. In Chinese, the word "tsai" in Mandarin dialect, and "choy" in Cantonese dialect, simply means "vegetable". Descriptive prefixes are added for further identification such as Pai-Tsai, which means white vegetable! Bok Choy refers to all leaf-heading vegetables! When Japanese, Thai, Cambodian or other Oriental names or dialects are used for the same vegetable, often with only slight variations on the Chinese name, as in "choi" or "joy", confusion can result! The names given here are often used in the Pacific Northwest by growers, brokers and buyers of these vegetables. All of the following have 10 chromosomes and generally intercross, and by some authors are all subspecies (ssp.) of Brassica rapa. Some subspecies, and taxonomic "variety" designations are given as found in:
The Nomenclature of Vegetable Crops. 1992. Lih Hung et al., Department of Horticulture, National Taiwan University, Taipei, Taiwan R.O.C.
TYPES AND VARIETIES (approximately 45 days for bunching types, 65-80 days for large heading types).
Chinese Cabbage (Brassica rapa var. pekinensis), often referred to as Pe-tsai. Two major types exist:
Chihli (elongated, cylindrical types about 4x18 inches): Jade Pagoda, Monument, Michihli. For trial: Statue. See note on bolting below.
Napa or Won Bok, (short, blunt, barrel shaped, about 5x12 inches): All Autumn, China Flash (both have season-long adaptability), China Pride. Others for trial: Cha Cha, China Express, Marquis, Nagaoka Early, Early Hybrid G, China Doll, Yuki; Tropical Delight and Kasumi (for warm areas). Bolting resistant (see also note under "temperature" section below): All Autumn, China Flash, Nerva, RS-5, Blues, Tango, Spring A-1, 50 Days. Winter and overwinter types for trial: WR Crusader, WR Green 60, 75 Days. Club root resistant: Chorus.
OTHER ORIENTAL GREENS
Pak-choi (Brassica rapa var. chinensis):
Synonyms: Pak Choy, Bok Choy, Bok-choi, Taisai, Celery Mustard or Spoon Cabbage, sometimes preceded by another proprietary name. These greens have dark green leaves and may have thick white, or thick light green petioles. Most of these are bolting resistant:
White petiole types: Joi Choi, Taisai. For trial: Pak-Choy White, Prize Choi, Lei Choi, Canton Pak Choi, Chinese Pak Choi White, Gracious.
Green Petiole types: Pak-Choy Green, Mei Qing Choi, Chinese Pak Choi Green. For trial: Pai-Tsai.
Baby Pak-choi, white petiole (for trial): Dwarf Pak Choi, Canton Pak Choi Dwarf Type. Green petiole: Shanghai. Since these are susceptible to bolting, delay field planting till mid-May or June (see note on bolting below).
Bunching Pak-choi: Mei Qing Choi (green petiole). When intended for use for "bunching", avoid using the "open" growth habit varieties such as Canton Pak Choi Dwarf, and evaluate others for an "upright habit" which would be more suitable for bunching. For trial: Joi Choi (white petiole), Autumn Poem (latter susceptible to bolting). For bunching, as for baby pak choi, open-pollinated varieties should also be tried.
B. rapa mustards:
Mustard Spinach or spinach mustard, Brassica rapa var. perviridis (L.); bunching greens, dark green leaves with slender green petioles: Komatsuna. For trial: Green in Snow, Green Boy. See note on bolting below, and delay planting accordingly.
Ta-tsai mustard, Brassica rapa; a thick-leafed, dark green, flat, compact rosette: Tatsoi.
Green Spray: Spherical plants with thin oblong or serrated leaves with long thin petioles: Mibuna (oblate leaves); Mizuna (serrated leaves).
Purple-stemmed, B. rapa: tender flower stalks and young leaves bunched just as flowers begin to open: Hon Tsai Tai. For trial: Tz-Tsai-Tai
Green-stemmed, B. campestris: Tsoi-sim
Green-stemmed, B. oleracea var. alboglabra: Chinese kale, or Chinese broccoli, a popular bunching green consisting of tender, thickened, flower stalks and young leaves, which are harvested when two or three flowers have opened: Kailaan (aka Gai Lohn), Green Lance Hybrid. Also: Broccolini, a hybrid of standard broccoli (Brassica oleracea var. italica) with Chinese kale (Brassica oleracea var. alboglabra), which resembles long, slender broccoli side shoots that are nearly ready to flower. The flavor has been described as similar to broccoli but sweeter and less pungent or as resembling asparagus. This hybrid was developed by Sakata Seed Co. and is grown and marketed exclusively in the United States by Mann Packing Co. and Sanbon LLC of California.
Brassica juncea leafy mustards: a group of "mustards" that have the chromosome number n=18. These are usually broad-leaved greens, sometimes red-leafed with green ribs:
Green-leaf: Namfong Round Leaved, Green Spray, Mizuna, Green-In-Snow (winter hardy). For trial: Horned Mustard, Miike Giant.
Red-leaf: Red Giant.
Note: Stem mustards (stems used in pickling) also fall into B. juncea.
This crop grows best in a cool, moist environment. Optimum temperature for growth in the first half of the growth period is about 68 F, and that for the second half (head formation) is 59 F. Under high temperature conditions, the plant grows slowly but it can tolerate temperatures above the optimum if there is enough soil moisture. Although all are somewhat frost tolerant, frost injury may occur with some types when the temperature falls from 26 to 18 F.
Bolting: Premature seed stalk development (bolting) of Chinese cabbage and Pak-Choi type greens is a result of vernalization of seedlings by cold temperatures when planted too early in spring. Bolting resistant varieties must be used, or delay planting till late April or May. Conditions predisposing plants to bolting are exposure of seedlings to temperatures of about 40 F for a week, or 50 F for two weeks, or prolonged temperatures below 55 F.
SEEDING AND SEED TREATMENTS
Chinese cabbage seed numbers approximately 160,000 per pound. Seed of the other Oriental greens mentioned above number between 12,000 and 18,000 per ounce. Pelletizing is not necessary with modern vacuum planters. Primed and coated seed is becoming popular. Consult your seed dealer about the availability of primed seed.
Use hot-water treated seed and fungicide treat seed to protect against several serious seed borne diseases. Hot water seed treatments are very specific (122 F exactly, for 25 to 30 minutes; the wet seed then quickly cooled and dried). The seed treatments are best done by the seed company, and can usually be provided upon request.
Chinese cabbage is planted from April through August.
Spring planting: as early as possible for early summer harvest. Bolting tolerant types may be seeded in the field in mid-April, others beginning in late May. All may be planted sequentially till mid-August.
Fall planting: middle of August for October and November harvest. Sow the seed directly in rows 2 feet apart and thin seedlings to 12-20 inches between plants within the row. Spacings vary with cultivar. Early maturing types require less space than the late types, and the Chihli type requires closer spacing than the Napa type. Seeds are sown at a rate of 8-10 oz/acre and hand thinned to one plant per location at the desired spacing.
For "baby" and "bunching" pak choi production, high populations (4 x 4 inch spacing) should be used to obtain needed growth habit and adequate yields.
Early spring field seeding may result in a high percentage of flower stalks. Therefore to produce a good summer crop, seedlings should be raised in the greenhouse and transplanted to the field after the risk of cold induction is minimized. For a late June and early July harvest, seedlings with 5-8 fully expanded leaves should be transplanted during May 10-20, and may be protected with plastic row covers. Use modular-grown transplants. Chinese cabbage is not normally transplanted as a bare-rooted plant. The transplant should be set in the soil to a depth of the first pair of leaves.
For the most current advice, see Nutrient Management for Sustainable Vegetable Cropping Systems in Western Oregon, available as a free download from the OSU Extension Catalog
NOTE: The following rates are general recommendations for western Oregon. It is advisable to do a soil test for each field to be planted.
Nitrogen: 150-175 (N) lb/acre.
Phosphorus: 70-150 (P2O5) lb/acre
Potassium: 130-175 (K2O) lb/acre
Sulfur: 30-50 (S) lb/acre
Disk 1/2 of the nitrogen and all the potassium and sulfur fertilizer into the soil before planting or transplanting, and band the other 1/2 of the nitrogen at planting or transplanting.
Note: Excess N and N applied after head formation can result in pepper spot. This is a physiological disorder that causes small black spots on the midribs of head leaves. Excess Mg, excess Mn, B deficiency, cauliflower mosaic virus, and storage at temperatures above 40 F may aggravate or cause similar symptoms.
Irrigate uniformly for vigorous tender growth. About 10-12 inches of water may be required depending on planting date, seasonal variation and variety.
Soil type does not affect the amount of total water needed, but does dictate frequency of water application. Lighter soils need more frequent water applications, but less water applied per application.
HARVESTING AND HANDLING
The University of California-Davis has a file on Minimal Processing of Fresh Vegetables that discusses film wrapping and other topics.
Approximate yield of napa Chinese cabbage is 450 cwt/acre. Pak Choi yields are approximately 225 cwt or 800-1000 boxes/acre.
Napa and Chihli Chinese cabbage heads are harvested when they reach appropriate market size (about 3-6 lbs), depending on variety.
Pak Choi and other greens may be harvested as individual heads similar to Napa cabbage. For specialty Oriental markets, these oriental greens are harvested immature and bunched 6-8 plants per bunch about 40-50 days after seeding. The time of harvest depends on one's specific market requirement.
To prevent Pak Choi petioles from cracking, cut and leave in the field for one hour before tying the bunches.
STORAGE (Quoted or modified from USDA Ag. Handbook 66 and other sources)
Store chinese cabbage at a temperature of 32 F and relative humidity of 95 to 100 %. Chinese cabbage can be stored 2 to 3 months under these conditions. Considerable losses are expected after 3 or 4 months of storage at 32 F. Storage life is shorter at higher temperatures. A low concentration (1 %) of oxygen was reported to be beneficial in extending the storage life. Outer diseased or injured leaves should be removed before the heads are stored. The heads should be packed loosely, and preferably upright, in crates. Spacing in storage should allow for air circulation.
Temperature control in storage of heads with pepper spot is critical as temperatures above 40 F aggravate the condition. Temperatures should be maintained at 32-34 F throughout storage and marketing.
Chinese cabbage is marketed in 35-lb cardboard boxes, or WGA crates of 80-85 lb.
Pak Choi and other Oriental greens are usually sold as individual heads, and may be packaged as Chinese cabbage above. For Oriental markets, bunches of 6-8 plants each are packaged 24-36 bunches per carton, depending on the item. Consult your buyers as to their preference in packaging and containers.