Asian Brassicas (Chinese broccoli, Chinese cabbage, bok choy and choy sum)

Introduction

Asian brassicas belong to the Brassica family—the Brassicaceae, which includes vegetables such as cabbage, broccoli, cauliflower, radish and turnips. Asian brassicas include Chinese broccoli (Brassica oleracea var. alboglabra Bailey), Chinese cabbage (B. pekinensis), bok choy (B. rapavar.chinensis) and choy sum (B. rapa var. parachinensis).

Chinese broccoli is also known as kai lan and gai lum. The whole plant can be eaten, but the older leaves and stems are generally stringy and discarded. Young leaves and stalks (15–20 cm high) with compact florets are selected. These parts of the plant are sweet and tender.

Depending on the cultivar, Chinese cabbage can vary substantially in appearance, from the short squat wong bok types to the long, slender rocket or michihili types. Chinese cabbage is the most frequently eaten vegetable in Asia. It is commonly eaten freshly cooked in stir fries and is often further processed as brined product or used in pickles such as kim-chi.

Chinese broccoli

Bok choy or pak choi does not form a true head. The whole plant (minus the roots) is eaten, with only the older leaves being discarded. Bok choy is eaten in both mature and ‘baby’ forms. After Chinese cabbage, it is the most commonly consumed Asian vegetable in Australia.

Choy sum is also known as Chinese flowering cabbage and tsoi sum. The whole plant can be eaten, including the normally yellow flowers. The height of the plant varies from 20 to 30 cm. The pleasant taste and cooking qualities of choy sum have made it the most common leafy vegetable in Hong Kong.

Asian brassicas are annual or biennial plants that are normally grown commercially as an annual. They have been grown successfully and are available in all Australian states. Farms vary from smaller urban market gardens, plots of around 1 to 2 ha, to larger and more remote holdings of 5–15 ha.

Markets and marketing

Asian brassicas are available nationally throughout the year in wholesale markets, Asian grocery stores and supermarkets. All are sold fresh or fresh-processed as a constituent of a salad mix. The marketing chain is relatively simple. Growers pick, wash and pack or bunch the product and deliver it to market on the same day as harvest. Chinese cabbage is packed into cartons; other species are sold in bunches. The fresh-cut salad market is more sophisticated: leaves only are harvested, washed, spun, refrigerated, either packaged for food-service,or sent to a secondary processor for inclusion in a salad mix, followed by packaging again and retail. Asian brassicas (usually in a baby-leaf form) that can be included ina salad mix include mizuna (B. rapa var. nipp osinica) , tatsoi (B. rapa var. rosularis) and Chinese mustard (B. juncea) . Recent price and volume data for Chinese cabbages and bunching lines at major wholesale markets are shown in Table 1.

Table 1. Asian brassica sales by volume and value at wholesale markets (2001)

It is estimated that around 80% of New South Wales and Victorian production passes through the central markets; in other states the proportion is closer to half.While export growth has stalled in recent years, Singapore, Hong Kong and Taiwan remain important outlets for Australian product. Australian exports face strong competition in these markets from an increasingly well-organised and low cost production base in China. Chinese competition based on low-cost labour also limits the potential of highly processed product such as pickles in both export and domestic markets. Fresh-processed salads containing Asian brassicas do not compete with product imported into Australia, which is restricted on phytosanitary grounds.

Production requirements

Asian brassicas are cool-season crops that prefer uniform moist conditions and full sunlight. The ideal temperature for growing is between 15 and 20° C. High temperatures and long days tend to induce bolting. Tropical cultivars of Chinese cabbage should be sought out for production in hotter climates. Most varieties tolerate light frosts.

Preferred soils are fertile, high in organic matter and moisture- retentive. Ideal pH is around 6.5 to 7.0 for bok choi, 5.5 to 7.0 for Chinese cabbage and 6.0 to 7.0 for Chinese flowering cabbage and Chinese broccoli. The addition of lime will help control club root, and planting into raised beds can prevent soft rots.

Asian brassicas are shallow rooted and require frequent light watering. This will also prevent the leaching of nutrients from the soil. Lack of moisture at any stage can promote bolting and poor-quality plants. Young plants are fragile and should be protected from the wind.

Varieties

Australian growers of Asian brassicas use hybrid seed in preference to open-pollinated seed or retaining seed from their own crops. Seed for most Asian brassica varieties is sourced from China and multiplied under contract in Australia. Popular and emerging varieties are shown in Table 2.

Table 2. Asian brassica varieties

Asian brassicas can be either sown directly from seed or transplanted into a fine well-prepared seedbed. Seed sowing is typically at a rate of two to three seeds per station 12–15 mm deep.Seedlings are hand thinned after germination. Chinese cabbage seeds are sown at a rate of 500– 750 g/ha, with plant spacing of approximately 35 cm. A similar distance is required between rows.

Chinese broccoli and choy sum are sown at about 0.6 cm in depth in rows about 30 cm apart and thinned to about 10 cm. Closer spacing will produce less fibrous plants with better eating quality. Bok choy is normally grown in rows spaced around 20 cm apart; large types like ‘Chinese White’ require more space and baby bok choi less.

Transplants are generally raised in a greenhouse or polyhouse for three to four weeks before planting in the field. Transplanting is more expensive than direct seeding but assists with environmental control during the early phases of the plant’s life.

Fertiliser requirements differ markedly between soil types; soil testing is the best way to determine the elements needed for crop production. In general terms Asian brassicas require large amounts of fertiliser, particularly nitrogen, potassium and phosphorus. Fertilisation often starts with an application of animal manure two weeks before planting followed by regular applications of nitrogen and potassium. Application of fertiliser through the watering system is effective. Over-fertilisation can result in soft rot and plant tip damage.

Maturation takes anywhere from 30 days for bok choy to 100 days for Chinese cabbage.

Pest and disease control

The availability of registered agricultural chemicals for pest and disease control in Asian brassicas is problematic.

Asian brassicas compete poorly with weeds in their first few weeks of life. Hand weeding or Dutch hoeing is commonly used to control weeds. A pre- and post- transplant herbicide application can also be necessary.

Major diseases of Asian brassicas include:

• clubroot—a soil-borne fungus that results in malformation of the roots and plant wilting during warm weather. Control is via crop rotation, fumigation, sanitation, maintenance of high soil organic matter and a pH above 7.3

• downy mildew—infected leaves develop purple, yellow or brown patches on the upper surface and white or grey downy fungal growth underneath. Older leaves develop dead spots. Control through improved ventilation to decrease humidity and avoid overhead irrigation
• white rust or white blister —small circular spots raised on both sides of the leaves, underside a mass of white powdery spores. Control through the removal of cruciferous weeds, crop rotations and ensuring that all plant residuals are removed or composted before the next crop is sown

• edema—wart-like structures on the underside of leaves. Control of the disorder can be achieved by not allowing the soil to become too wet and improving the ventilation of polyhouses.

Major pests of Asian brassicas include:

• aphids—live on the underside of leaves. Affected plants will wilt, look distorted and curled. Aphids are also vectors for viruses. Control cruciferous weeds in the vicinity of Asian brassicas
• caterpillars—will attack and severely damage brassica crops. Many species, especially diamond-back moth, have developed resistance to common control chemicals and integrated pest management is recommended
• snails and slugs—eat whole young plants and are especially active during mild damp weather. Control with pellets.

Harvest and post­harvest

Harvest should occur in the cool early morning. Asian brassicas are hand-harvested at the base with a knife. Old or damaged outer leaves are trimmed off and the butt trimmed flush at the base. All blemishes and defects should be removed.

Harvest should occur before the outer leaves become yellow and the plant becomes fibrous.

For the fresh-cut salad industry, leaves can be either mechanically or hand harvested. Leaves are cut at the petiole. Leaves are often washed in sanitised water, spun- dried, packaged and cooled. Brassicas should be stored at 2–5°C. Product should be covered with plastic sheet to maintain high humidity and keep out air currents from the refrigeration system. Bunching lines can be stored for up to a week; Chinese cabbage will store for longer periods. Brassicas should be handled carefully as they are easily damaged.

Financial information

Asian brassicas, especially bunching types, are often grown on rented land in the urban fringe of capital cities, with few establishment costs. They offer a low-entry cost enterprise for newly arrived migrants. Chinese cabbage tends to be grown on larger more remote farms and requires greater mechanisation.

Establishing a cost of production and generating crop gross margins is limited by the availability of data and the cultural expectations of growers. For example, growers in New South Wales of Vietnamese origin do not consider labour to be a cost of production. Profit is based on the gross return of the crop minus the cost of materials (seed fertiliser, chemicals, rent, etc). This perception of production returns is exacerbated by difficulties in obtaining labour costs and yield data from growers wary of revealing financial information.

Typically the extended family provides the farm labour and appropriately priced external labour is difficult to secure.

The industry is experiencing price pressure as supply continues to grow and domestic and export markets mature. Strong price competition has placed downward pressure on product quality. The general perception is that an acceptable profit margin is still available on most crops but thatit is insufficient to retain the second generation of growers. Representative yield, unit prices and gross returns are shown in Table 3 below.

Table 3. Yield and Gross Income Estimates

Key messages

• Asian brassicas are cool- season crops that prefer moist conditions and full sunlight.
• Seed from most Asian brassica varieties is sourced from China and multiplied under contract in Australia.
• The industry is experiencing price pressure as supply continues to grow and domestic and export markets mature.

Key statistics

• Australia produced over 15,125 t of Asian brassicas in 2001.
• The gross value of sales of Asian brassica produced in Australia in 2001 was over $19 million.
• After Chinese cabbage, bok choy is the most commonly consumed Asian vegetable.

Acknowledgements

Acknowledgment is made to Stephen Moore, Wendy Morgan, Bruce Tomkins, Paul Daly and Mandy Chew, authors of the chapters on Asian brassicas in the first edition of this publication.

Key contacts

Dr David Midmore, Professor of Plant Sciences, School of Biological and Environmental Sciences, Central Queensland University, Rockhampton QLD 4702

Tel: (07) 4930 9770

Email: d.midmore@cqu.edu.au

Dr Vong Nguyen

NSW Agriculture Gosford Horticultural Research and Advisory Station

Tel: (02) 4348 1927

Email: vong.nguyen@agric.nsw. gov.au

Vynka McVeigh

Research Officer, Department of Agriculture Western Australia

PO Box 123 Bunbury Western Australia 6231

Michael Clarke

AgEconPlus Pty Ltd 44 Barons Crescent Hunters Hill 2110 Tel: (02) 9817 5888

Email: Clarke@AgEconPlus. com.au

Dr Tim O’Hare

Department of Primary Industries and Fisheries Gatton Research Station Gatton QLD 4343

Tel: (07) 5466 2257

Email: Tim.O’Hare@dpi.qld. gov.au

Key references

Central Queensland University http://www.ahs.cqu.edu/ info/science/psg/AsianVeg/ CinF1Cabb.html viewed Feb. 2004.

Hassall & Associates (2003) Asian Vegetable Industry Situation Assessment, Pub. no. 02/16 8. RIRDC, Canberra.

Morgan, W, & Midmore, D. (2003) Chinese Broccoli in Southern Australia, Pub. no. 02/161. RIRDC, Canberra.

O’Hare, T.J., Able, A.J., Wong, L.S., Prasad, A., & McLaughlin, R., (2001) Fresh-cut Asian Vegetables – Pak Choi as a

Model Leafy Vegetable. ACIAR Proceedings No. 105, p. 113–116.

About the Author

Michael Clarke is an experienced agricultural economist,

researcher, policy analyst and business planner. His work for RIRDC includes an Asian vegetable industry situation assessment, a review of hydroponics as an agricultural production system, financial analysis of new and emerging rural industries, market opportunities for Australian- grown jojoba and an audit of the Australian organics industry. In 2004 Michael prepared a business development strategy for a Cambodian vegetable growers cooperative and was part of a team that reviewed the efficiency and effectiveness of Horticulture Australia Limited. Michael is principle consultant for AgEconPlus Pty Ltd.

Disclaimer

Whilst every care has been taken in preparing this article,neither RIRDC , the Authors or Informed Farmers accept any liability or responsibility for decisions or actions taken as the result of any data, information, statement or advice, expressed or implied, contained in this article. Readers should make their own detailed inquiries and obtain professional advice before making any commercial decisions based on information contained in this article.