Information sheet for home gardeners on growing Oriental leafy greens

Ebesu, Richard

ScholarSpace at University of Hawai'i at Manoa

Published by the College of Tropical Agriculture and Human Resources (CTAHR) and issued in furtherance of Cooperative Extension work, Acts of May 8 and June30, 1914, in cooperation with the U.S. Department of Agriculture. Andrew G. Hashimoto, Director/Dean, Cooperative Extension Service/CTAHR, Universityof Hawaii at Manoa, Honolulu, Hawaii 96822. An Equal Opportunity / Affirmative Action Institution providing programs and services to the people of Hawaii withoutregard to race, sex, age, religion, color, national origin, ancestry, disability, marital status, arrest and court record, sexual orientation, or veteran status.CTAHR publications can be found on the Web site <http://www.ctahr.hawaii.edu> or ordered by calling 808-956-7046 or sending e-mail to ctahrpub@hawaii.edu.Home Garden VegetableMay 2004HGV-10*Home Garden Oriental Leafy GreensRichard Ebesu, Department of Plant and Environmental Protection Sciences*This document replaces Hawaii Cooperative Extension ServiceHome Garden Vegetable Series no. 10, “Mustard Cabbage,” 1978.**For information on sampling soil and arranging for its analysis byCTAHR-ADSC, see the CTAHR publication Testing your soil—whyand how to take a soil-test sample, available at www.ctahr.hawaii.edu/freepubs under “Soil and Crop Management,” or from UH-CTAHRCooperative Extension Service offices statewide.Awide variety of Oriental greens are prepared asvegetables, and many are available to gardeners inHawaii. These greens belong to several different spe-cies, and there are several varieties of each, making theirclassification a bit confusing. Brassica rapa (synonym,B. campestris) is the predominant species, with severaldifferent varieties. Chinese cabbage is Brassica rapa var.pekinensis, which includes subtypes that form heads,known as won bok and Napa cabbage, as well as loose-headed types. Mibuna and mizuna greens are B. rapavar. nipposinica; these plants form fairly large clumpswith many stems bearing narrow leaves.Pak choy (Brassica rapa var. chinensis) includestypes called white cabbage, spoon cabbage, choy sam(Singapore), pechay (Phillipines), and taisai and shirona(Japan), as well as others. The preferred type of pak choyhas dark green leaves and long, white, somewhat widepetioles. Some other varieties have shorter, slightly greenpetioles. Some varieties are grown for the floweringstems rather than the leaves.The species Brassica juncea includes the typescalled kai choy in Hawaii, the mustard greens grown inthe southeastern United States, and the rai and sarsongrown for oilseed in India and Pakistan. It is also calledbrown mustard and Indian mustard. Its forms are vari-able, with leaves that are either smooth or hairy, entireor divided, and petioles that are either narrow or wide.Compared to pak choy, its leaves are lighter green andits petioles are green and shorter.The flowering brassicas include choy sum (B. rapavar. parachinensis), purple flowering pak choy (B. rapavar. purpurea), and Chinese broccoli or kailaan (B.oleracea var. alboglabra).The oriental greens form larger plants and are slowerto bolt (flower) when temperatures are cool, that is, whengrown at Hawaii’s higher elevations or during the win-ter season, but some can be grown in warm conditions.Won bok may not form heads in warm seasons.VarietiesThe most common kai choy variety in Hawaii is theWaianae strain. It has wide green petioles, and the innerleaves form a slight head. The Mainland variety OsakaPurple has loose, purple leaves. Varieties of other orien-tal greens come from Taiwan, Japan, or the mainlandUnited States.Preparing the soil: amendments and fertilizerOriental leafy green plants grow best in well drained,moderately acidic to neutral soil (pH 6.0 to 6.8 is opti-mum) with a good level of soil organic matter. Have thesoil analyzed to determine the soil pH and whether anysoil amendments (including lime, dolomite, and phos-phate) are needed. A soil analysis is particularly recom-mended for new garden sites. A “standard” soil analy-sis, which measures soil pH and available soil phospho-rus, potassium, calcium, and magnesium, is relativelyinexpensive and can be done by the CTAHR Agricul-tural Diagnostic Service Center** or a commercial labo-ratory (preferably one having experience with Hawaii’ssoils).Soil with pH below 5.5 requires application of agri-cultural lime to increase the pH to a level more favor-able for plant growth. Soil in high-rainfall areas oftenrequires lime to increase the calcium supply.UH-CTAHR Home Garden Oriental Leafy Greens HGV-10 — May 20042Low levels of available soil phosphorus limit plantgrowth in many of Hawaii’s soils. Both lime and phos-phate fertilizer must be mixed thoroughly into the sur-face 6–8 inches of the soil before planting.Home garden productivity can usually be increasedby amending the soil with organic matter, such as com-post or well rotted animal manure (see the CTAHR pub-lications Backyard composting—recycling a naturalproduct and Composted animal manures—precautionsand processing). If a suitable material is available, makean annual application to the garden of 1–3 inches spreadover the soil and mixed into the surface 6–8 inches. Ifthe material is in short supply, its application can be lim-ited to the area within 6–10 inches from the plantingrow or spot.To ensure adequate levels of the major plant nutri-ents, include a general fertilizer when preparing the gar-den before planting. Commonly available rapid-releasefertilizer formulations suggested for vegetables are 16-16-16 (“triple-16”) and 10-20-20 (these numbers referto the percentages of nitrogen, phosphate, and potash inthe fertilizer). Commercial growers often figure on ap-plying a total of 150 pounds of N per acre to a crop oforiental leafy greens. On a 100 square-foot (sq ft) basis,this is equivalent to two applications (one preplanting,the second after thinning the crop) of 13⁄4 pounds of 10-20-20 or 1 pound of 16-16-16 per application. Garden-ers who prefer to use slow-release formulations willapply all of the nutrients before planting. Preplantingfertilizers should be mixed well with the garden soil.Soil phosphorus can increase to an undesirably highlevel after long-term application of high-phosphate fer-tilizers, such as 10-30-10. If this is part of the garden’shistory, a soil analysis should be done to check the phos-phorus level. If it is in excess, a zero-P formulation canbe created by mixing equal amounts of urea and muri-ate of potash to produce a formulation that is about 23-0-30. For the 100 sq ft basis fertilizer schedule men-tioned above, about 3⁄4 pound of this fertilizer would beapplied in each of two applications.PlantingPlant seeds directly in the soil 3–4 inches apart in rowsspaced 12–15 inches apart. Three to four weeks afterplanting, thin the seedlings to 10–12 inches apart forlarger plants such as kai choy, won bok, and mibunaand 8–10 inches apart for pak choy. If thinning is de-layed, the plants may become spindly and leggy and maybolt before forming a useful plant.Fertilizer application to the growing cropAfter thinning the seedlings, apply the second dose ofgeneral fertilizer. Divide the amount of fertilizer beingapplied into small doses according to the number ofplants in a 100 sq ft garden area. Apply each dose 6–8inches from the base of each plant. Some gardenersspread the fertilizer on the soil surface, but others be-lieve it is best to use a trowel to incorporate it 2–4 inchesinto the soil, using care to minimize damage to the plantroot system. If planting in rows, distribute the fertilizeralong a trough 6–8 inches from the base of the plantsand cover it with soil. One application of fertilizer afterthinning should be sufficient for leafy greens, whichusually are harvested about 45–50 days after seeding.Irrigate after the application. Liquid fertilizers are alsosuitable for postplanting applications.Overapplication of fertilizer may result in plants thatare too succulent and may develop tip burn under warmconditions.IrrigationA steady supply of water is important for good plantgrowth and quality. Insufficient moisture may result intip burn, slow growth, and less tender leaves. Irrigate asnecessary to maintain available soil moisture, but avoidsoil waterlogging. To minimize leaf disease, avoid wet-ting the plant when applying water. If possible, irrigateonly the soil using furrows, drip lines, or soaker hoses.If using overhead (sprinkler) irrigation, do it in the morn-ing so the plants dry quickly as the day warms.Insect managementThe most common insect pests are cutworms, aphids,thrips, cabbage webworms, loopers, and spider mites.The caterpillar pests can be controlled with insecticideproducts containing the bacteria Bacillus thuringiensis.Aphids, thrips, and mites can be suppressed with insec-ticidal soaps. When using a pesticide product, read thelabel to make sure it is approved for use on the crop andthe pest, and follow the label directions.3UH-CTAHR Home Garden Oriental Leafy Greens HGV-10 — May 2004Disease managementThe most common diseases of oriental leafy greens aredamping off, mosaic, white rust, and soft rot. Dampingoff and soft rot are soil borne-diseases and can be avoidedby planting in clean soil. Addition of compost may helpto combat soil-borne diseases. Avoid white rust by irri-gating as suggested above to minimize wetting the plantsand by promptly removing diseased plants that couldserve as a source of fungal inoculum.HarvestIf white rust is a problem, harvest when the plants areyoung, before infection occurs. “Baby greens” are alsoharvested early. Otherwise, oriental leafy vegetableplants are harvested as they near maturity, about 45–50days after planting, before the flower stalks appear. Cutoff the whole plant at ground level and remove any dam-aged outer leaves. For flowering types such as choy sum,the flowering stalks are harvested just before the flow-ers open.Seed availabilitySeeds of the Waianae strain of kai choy are availablefrom the CTAHR Agricultural Diagnostic Service Cen-ter Seed Lab on the UH Manoa campus and from somegarden stores. Other varieties can be found in gardenstores and seed company catalogs. CTAHR Seed Laborder forms can be obtained online at <www.ctahr.hawaii.edu/seed> or from Cooperative Extension Ser-vice offices statewide.

Home Garden Oriental Leafy Greens

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Home Garden Oriental Leafy Greens

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