Rural Industries Research & Development Corporation

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Introduction

Chinese chard has been grown successfully and is available in all Australian States. It has characteristic two-toned leaves with bright and/or ivory white leaf stalks topped with dark green leaves. The only exception is Shanghai Chinese chard, which has light green leaves and leaf stalks. The flowers of Chinese chard are bright or pale yellow about 1 cm long. The seeds are round, dark brown and weigh approximately 3 g/1000 seeds.

In Australia, Chinese chard is a very important leafy vegetable making up about 10% of the total Asian vegetables used by volume, second only to Chinese cabbage. Chinese chard is easy to grow, produces relatively high yields and is very nutritious.

Markets and marketing issues

Chinese chard is available at most major wholesale markets and Asian grocery stores throughout the year in Australia. In Sydney, the average wholesale price range is between $0.50 and $1.00/bunch. Similarly, the Melbourne Market average wholesale price was between $0.50 and $1.00/bunch. The average retail price in and around Melbourne was between $1.50 and $3.00/bunch.

Chinese chard has been given a high industry priority for expansion for the Australian fresh market on the basis of existing market and production information. It was also listed as one of the top five Asian vegetables for the three major trading channels: Asian restaurants, Asian grocery stores and Australian supermarkets.

Production requirements

Chinese chard can be grown in a wide range of soils, but prefers fertile, high organic matter and moisture-retentive soils (e.g. rich loamy soil). The ideal soil pH is around 6.5-7.0 and lime should be added if it falls below a pH of 6. Adding lime to the soil profile is also thought to help reduce the incidence and severity of clubroot if present. Soft rots can also be prevented by preparing raised beds with improved drainage and improved air circulation.

Chinese chard is shallow-rooted like most other brassica crops and requires frequent watering for optimum growth. Lack of moisture at any stage can promote bolting and poor quality plants. The water should be applied lightly and frequently, to reduce the chance of leaching soil nutrients and encourage healthy plant growth. Young plants should be protected from the wind as even the leaves of mature plants can be damaged by strong winds.

Key Statistics

Varieties

1) The `Chinese White Bok Choy' is a sturdy-looking variety with thick green leaves curling outwards. The leaf stalks are bright white, curved slightly and thin. The plants tend to reach a height of about 30 cm at maturity. Although they vary in their cold tolerance and have a tendency to bolt, they are vigorous. An example of a highly productive hybrid is `Joi Choy'.

2) The green leaf stalk type, `Shanghai Bok Choy', has leaf stalks which are light green in colour, broad, flat and widen at the base like the other bok choys. They are harvested at a height of around 15 cm. They are very hardy and able to grow all year round at temperatures between 18 and 21°C. A popular variety is `Mei Qing'.

3) The `soup spoon' type has thinner leaves and leaf stalks. The leaves are lightly cupped and ladle-like while the leaf stalks are white and semi-circular. They grow to a height of 45 cm and there are shorter forms available. They are vigorous and versatile with good tolerance to cold and heat. Varieties include `Japanese White Celery Mustard', `Nikanme', `Seppaku' and `Tai Sai'.

4) The `squat' or `Canton' variety is the most compact. It is short with convoluted dark green leaves. The leaf stalks are white, short and thick. They can be harvested as baby bok choy or left to reach maturity. They are best adapted to warm weather and very apt to bolt in the cold weather.

Agronomy

Chinese chard can be sown directly or transplanted into a well-prepared, raised bed. Spacing varies according to the type, variety used and size of plant required. The large types like `Chinese White' require 45 cm between each plant. The average within-row spacing for medium-sized varieties would be 18 to 23 cm and the small varieties, 2.5 to10 cm apart. Rows should be 18 to 30 cm apart.

Seedlings can be raised in a heated environment at a minimum temperature of 18°C, and hardened off before transplanting. Transplants reduce the time plants are grown under adverse conditions, reducing the chance of bolting and the time to harvest. Commercial production of Chinese chard in greenhouse and polyhouse structures has been successful all year round. The seed is usually germinated in seedling trays at about 20°C and after emergence the temperature is reduced to about 10°C or less. The seedlings are generally transplanted in the greenhouse structure after 25 to 30 days of growth and if possible the temperature is raised to about 20°C a week after planting.

During late autumn to early spring when the weather is cool, only cold-tolerant types and cultivars should be grown, such as the Chinese White Bok Choy and soup-spoon types. Heat-tolerant varieties such as the Shanghai Bok Choy and Canton types, can be grown during summer conditions or in heated polyhouses.

On sandy or light soils, the highest yield of Chinese chard has been achieved with 200 kg/ha nitrogen and at the closest plant spacing of 0.1 m ¥ 0.3 m. The plant spacings used were 0.1 m, 0.2 m, 0.3 m and 0.4 m with 0.3 m between rows. At 400 kg/ha of nitgrogen yields actually decrease and the incidence of soft rot damage increases. The fertiliser and spacing does not significantly affect the time Chinese chard takes to reach maturity.

Pest and disease control

The major diseases of concern when growing Chinese chard, are as follows:

Clubroot (Plasmodiophora brassicae) is distributed worldwide and is a major disease of all brassica crops. The soil-borne fungus develops slowly, entering the root hairs and forming club-like malformations on the roots. The plants become stunted and wilt during warm weather. Good management practices can help control clubroot. Common practice is to use a combination of long plant rotations with non-hosts, maintenance of a soil pH at 7.3 or above, fumigation, sanitation and maintenance of a high soil organic matter. Farm hygiene is very important because it helps prevent the movement of clubroot from infected soil into clubroot-free areas. Future control measures may use combinations of chemicals, nutritional programs, rotation and clubroot resistant varieties.

Downy mildew (Peronospora parasitica) is also a worldwide major disease of brassica crops. Infected leaves develop purple, yellow or brown patches on the upper surfaces and white to grey downy fungal growth underneath. Older leaves show signs of small necrotic areas that look like small black specks. During moist conditions the specks may enlarge to form large black patches. Plants should be kept well ventilated to reduce the humidity and the risk of downy mildew. Overhead irrigation should be avoided where possible. Cruciferous weeds should be controlled.

White rust or white blister (Albugo candida) is distributed worldwide and is a less common disease of brassica crops, radish and other mustards. Symptoms include small circular spots raised on both sides of the leaves. On the underside of leaves, a mass of white powdery spores develops. Yellowish to green spots also develop on the top surface of leaves. White rust can be controlled by removing any cruciferous weeds, long plant rotations with non-hosts and by ensuring that all plant residues are completely decomposed before transplanting new crops.

Edema (oedema) is a physiological disorder with symptoms that resemble small warts; these can join together to form a ridge. Usually they are found on the underside of leaves. The disease can occur when soil is warm and wet, but the air temperature is cool. The disease is favoured by prolonged periods of high humidity, which can occur in poorly ventilated polyhouses or glasshouses. Control of the disorder can be achieved by not allowing the soil to become too wet and in polyhouses by having good ventilation.

The major pests of concern when growing Chinese chard, are as follows:

Aphids (Brevicoryne brassicae) can feed on a large number of plant hosts. They have piercing and sucking mouth parts which they use to get sap from plants. Aphids can be found underneath leaves, and where they like to feed on new shoots and buds. Parts of the plant may wilt, look distorted and curled. The aphids can also act as vectors for a number of viruses (e.g. turnip mosaic), causing even greater damage. Cruciferous weeds should be controlled as they host aphids.

Caterpillars (the larvae of moths and butterflies) will attack and severely damage brassica crops. Examples include the large and small cabbage white butterflies (Pieris rapae), the diamond back moth (Plutella xylostella) and the green looper (Chrysodeixis eriosoma). Many chemicals have been used to control caterpillars and resistance to some chemicals has developed, particularly for diamondback moth. Appropriate strategies such as IPM should be used for controlling caterpillars and in particular diamondback moth.

Snails and slugs (Class Gastropoda) are attracted to the succulent leaves of all brassica crops. They are of major concern to growers, because they eat whole young plants and can severely damage older plants. The greatest damage occurs during mild and damp weather, when snails and slugs are most active. Snail and slug pellets are the most commonly used form of control.
 

Harvest, handling and packaging, storage, 
postharvest treatments and processing

Chinese chard is usually hand-harvested at the base with a knife. Any old or damaged outer leaves are trimmed off and the butt trimmed flush at the base. There should be no blemishes or defects of any kind. Chinese chard can be ready to harvest 35–55 days after sowing.

Yields average about 15 t/ha. Chinese chard should be harvested well before the outermost leaves turn slightly yellow, which is before the plant fully matures and becomes fibrous. The plants can bolt before maturity and should be harvested when there is any evidence of a flower stalk.

Chinese chard should be harvested in the cool part of the day and handled carefully as they are prone to physical injuries, such as bruising of the leaf stalk. As it is susceptible to wilting, Chinese chard should be used fresh as possible. In Australia, Chinese chard are bunched in groups of 2–3 plants. Bunching is not a good practice as the string/band used to tie the bunch together causes damage. The white-stemmed varieties can be stored at 0–1°C with 85–100% humidity for a week while the green-stemmed variety can be stored for a little longer. Chinese chard can last up to 30 days in modified atmosphere packaging (MAP). Little is known about the effects of type and cultivar on storage life.

Economics of production

Key contacts
Stephen Moore
Dept of Natural Resources and Environment
P.O. Box 103, Geelong, Vic. 3220
Phone: (03) 5226 4667
Fax: (03) 5226 4725

Mandy Chew
Institute for Horticultural Development
Private Bag 15, South Eastern Mail Centre,
Vic. 3176
Phone: (03) 9210 9222
Fax: (03) 9800 3521

Dr Wendy Morgan
Institute for Horticultural, Development
Private Bag 15, South Eastern Mail Centre,
Vic. 3176
Phone: (03) 9210 9222
Fax: (03) 9800 3521
 

Key references

Cucuzza, J., Dodson, J., Gabor, B., Jiang, J., Kao, J., Randleas, D., Stravato, V. and Watterson, J. (1994). Crucifer Diseases: a practical guide for seedsmen, growers and agricultural advisers. Cal Graphics, California, USA.

Lee, B. (1995). Audit of the Australian Asian Vegetable Industry. Rural Industries Research and Development Corporation.

Hill, T.R. (1990). The effect of nitrogenous fertiliser and plant spacing on the yield of three Chinese vegetables—Kai lan, Tsoi sum and Pak Choi. Scientia Horticulturae, 45, 11–20.

Larkcom, J. (1991). Oriental vegetables: the complete guide for garden and kitchen. John Murray, London.