Rural Industries Research & Development Corporation

The New Rural Industries
A handbook for Farmers and Investors

Chinese broccoli

Introduction

Chinese broccoli (Brassica oleracea L. var. alboglabra Bailey) belongs to the Crucifer family, which includes vegetables such as cabbage, broccoli, cauliflower, radish and turnips. It has other common names such as kai lan and gai lum. Chinese broccoli is also closely related to the European broccoli and the Portuguese `Couve Tronchuda' cabbage. It was probably introduced into China from the Mediterranean during ancient times.

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, because they are sweeter and more tender.

Chinese broccoli is a perennial plant that is often grown commercially as an annual. The leaves of Chinese broccoli are oval, glabrous and bluish/green. The average spread of Chinese broccoli is between 25 and 37 cm and depending on the variety, it grows to about 45 cm in height.

Markets and marketing issues

In Australia, Chinese broccoli is available at most major wholesale markets and Asian grocery stores throughout the year. The wholesale price ranges between $0.50 and $1.00/bunch. The Melbourne Markets average wholesale price is between $0.90 and $1.50/bunch. The average retail price in and around Melbourne is between $1.00 to $1.60/bunch.

Chinese broccoli is widely sold and is one of the main Asian vegetables grown in New South Wales and Victoria.

Production requirements

Chinese broccoli is a cool-season crop and has some frost tolerance, preferring uniform conditions that are not too dry, wet or shady. Young plants should be protected from the wind.

Chinese broccoli is shallow-rooted like most other brassica crops and requires frequent watering for optimum growth. Water should be applied frequently but lightly. Light watering reduces the chance of leaching nutrients out of the soil. Frequent watering encourages healthy plant growth.

The amount of water needed is influenced by soil type, with sandy soils draining very quickly and requiring more frequent watering than other soils. The ideal soil type for vegetable production is fertile and has good drainage along with a high content of organic matter. The soil pH should be between 6.0-7.0 and should not fall below 5.0.

Varieties

Chinese broccoli varieties are differentiated by their flowering period, so they are conveniently classified into early, mid and late season. Different varieties may have white or yellow flowers or a wrinkled leaf; the major commercially grown varieties have white flowers. Hybrids (e.g. F1 Green Lance) are generally more vigorous than the common white-flowered varieties. A much smaller yellow-flowered variety (Chinese Yellow Broccoli) is recommended for summer production.

Chinese broccoli can be grown successfully all year provided different varieties are used in accordance with the season or climate. Matching the varieties with different seasons or climates can be difficult: there is little information on varieties, seasons can change yearly and climates can be markedly different from place to place. For example, summer-grown Chinese broccoli was bitter in taste and disliked by consumers. The poor quality came from using the wrong varieties for that time of year.

Agronomy

The rates of fertiliser for optimum crop development can differ markedly between soil types. Soil testing is the best way to determine what is needed. Two suggested fertiliser mixes for Western Australian soils, are as follows :

1. Sandy Soils. A base dressing of 50 m³/ha poultry manure, 1.25 t/ha superphosphate and trace elements. A side dressing of 150 kg/ha Agran 34-0 and 150 kg/ha muriate of potash should be applied about one, three and five weeks after emergence

2. Medium and Heavy Soils (Poor fertiliser history). Base dressing of superphosphate
(2 t/ha), muriate of potash (600 kg/ha) and trace elements. A side dressing of Agran 34-0 (200 kg/ha) should be applied about one week after emergence and Agran 34-0 (100 kg/ha) about three and five weeks after emergence

In trials of three forms of base fertilisers (each supplying 67 kg N/ha) on Chinese broccoli, the best results were obtained from:

(1) commercial organic-inorganic fertiliser mix (3.5% N, 3.5% P and 2.7% K) at a rate of 1900 kg/ha,

(2) well-rotted cow-manure (1.0%N) at a rate of 1000 kg/ha, plus inorganic fertiliser (15% N, 6.5% P and 12.5% K) at a rate of 380 kg/ha, and

(3) inorganic fertiliser (15% N, 6.5% P and 12.5% K) at a rate of 447 kg/ha.

The differences between fertilisers were associated with the organic matter content which produced a better soil structure. Fertilisers with too much organic matter (e.g. 45%) reduced the availability of nutrients and performed poorly.

Chinese broccoli can be sown directly or transplanted in rows about 3 cm apart and spaced/thinned to about 10 cm. Seed can take 4-10 days to emerge from a sowing depth of 0.6 cm during autumn and 3-6 days in summer. Transplants are generally planted 3-4 weeks after sowing the seed. The growing time from seeding to harvest averages 50 days during February to December.

Chinese broccoli can be grown close together to give a more desirable product, which is not large and tough stemmed. The closer spacings slow down the maturation process and produce less fibrous plant tissue, which is indicated by a high leaf-area index. If the inter-plant spacing is decreased, there is a reduction in the crude fibre content and an increase of marketable and total yields.

Plant spacings reduced from 30 cm to 20 cm and 10 cm, result in a progressive increase in fresh-weight yield/ha. However, a lower mineral content is found in the plants at the closest spacing of 10 cm. The lower mineral content results from increased competition for nutrients. Transplants may reduce the competition for nutrients between plants.

In Malaysia, transplants when harvested at six weeks after transplanting (eight weeks after sowing), yield about 53% more marketable fresh-weight and with a higher mineral content than the direct-seeded plants of the same age (8 weeks). Additional fertiliser should also reduce the competition for nutrients between plants.

Pest and disease control

See Chinese chard.

Harvest, handling and postharvest treatments

Chinese broccoli matures quickly without much attention. Its shoots can be ready to harvest in 10 weeks from sowing during autumn and 8-9 weeks from sowing during summer. On average it takes 65 days from sowing to maturity. Chinese broccoli should be harvested frequently, especially during the hot weather, to prevent premature bolting and to prevent the shoots from becoming tough.

The time of harvest is critical. The plants are generally harvested with a knife well before any buds begin to open and no later, because then the flavour is at its best. The flowers may open only slightly without spoiling the flavour. The main flower stalk should be cut relatively short to allow sufficient regrowth for further harvests. A liquid feed after each cut may be beneficial and other shoots grown beyond the first three cuts are generally not worth harvesting.

The time of harvest of most Asian vegetables is critical for high quality produce. Harvesting in the cool of the morning is preferred because it reduces moisture stress. Once picked, the plants are bunched into groups of five to seven and tied. The main stem should be long
(10-15 cm) and thick in diameter (1.5-2.0 cm at the base). Chinese broccoli should be presented free of roots and with or without flowers. The plants should be fresh and free from any defects, foreign matter and chemical residue.

Harvested plants should be rapidly cooled as soon as possible to storage temperature (0-2°C) without freezing. A high relative humidity (90-100%) is important especially during the pre-cooling phase. If not stored under these conditions, Chinese broccoli will quickly dry out and wilt, becoming unsaleable.

Economics of production, Key contacts, Key references, and Key statistics

See Chinese chard.