Leafy greens are one of the great unsung joys of Chinese eating. Often mentioned only as an afterthought on restaurant menus, usually as 'seasonal vegetables’, they are a vital and essential part of the Chinese diet and no supper table is complete without them.
Choy Sum is one of the most popular vegetables in Hong Kong and Southern China. It is now also widely used in the western world. It is instantly recognisable, used in various stir-fry dishes and soups in Cantonese cuisine. The flavour of Choi Sum can be described as midway between cabbage and spinach, it tends to be milder in younger leaves, and develops a little 'kick' in its older leaves. It is often described to be along the lines of a sweet, less bitter, broccoli raab.
The absolute fabulous thing about this gorgeous green is, you use the whole plant: Flowers, buds, leaves and stems. If allowed to mature and bolt, yellow flowers will shoot and the plant becomes sweeter and more succulent.
Choy Sum 'Purple Stem' is a vigorous and productive 80 day type. Suitable for autumn production it can withstand temperatures below 0°C (32°F). Quick to break into flower stems, but still makes a large frame with good eating quality stems. The stems are purple red with distinctive flavour and the leaves are rounded and mid-green in colour. The plant height is about 30cm (12in) with a spread of 35cm (14in).
Grow Choy Sum in full sun in cool regions and in partial shade in warm regions. Plant in well-worked, well-drained but moisture retentive soil rich in organic matter. Add aged compost to planting beds before planting and side dress crops with compost again at midseason. It can be grown in containers at least 20cm (8in) across. Plants are sensitive to heat so move containers into shade when the weather warms.
Choy Sum is a cool season crop preferring uniform conditions, moderate moisture levels and reasonable sunlight. When seasons are not too extreme, it can be grown all year round. Green varieties are not frost tolerant; however, the purple-flowered variety can withstand temperatures below 0°C (32°F). The optimum growing temperature for minimum time to harvest is between 15°C (59°F) and 25°C (77°F).
In temperate climates Choi Sum can be sown early with protection (February to April). It can be sown directly outdoors after the risk of frost has passed (from May to September). Late summer sowings should occur 6 weeks prior to the first frost.
For warmer climates, higher temperatures may result in thinner, tougher and less sweet shoots or may lead to bolting so it may be best to plant from mid to late spring and early autumn. Phasing the sowing will extend the cropping period.
Sowing: Sow in spring through to autumn
Choi Sum does not transplant well. Seeds are best sown directly in the garden as transplanted seedlings may be shocked into bolting to seed. They can be started early indoors, but should be started in biodegradable peat or paper pots which are easily set directly into the garden.
Sow seeds direct into finely raked, moist, weed free soil. Make a drill 12mm (½in) deep and lightly water. They can be grown at plant spacings varying from anything between 2.5cm (1 in) for baby leaf or 10 to 20cm (4 to 8in) for wholehead production, and row spacings of between 7 to 30cm (3 to 12in). Seeds germinate in 6 to 10 days at 13 to 24°C (55 to 70°F). Thin out weakest seedlings to leave one per station.
Choy sum grows in a wide range of soil types from light sands to clay loams but prefers fertile, well-drained soils. It does not tolerate dry conditions or water logging. If drainage is an issue or on heavier soils, plants should be grown on raised beds. The ideal soil pH is 6.0 to 7.0, it should not fall below 5.0 although pH readings greater than 7.0 are desirable for club root control.
Protect seedlings from birds. Added protection from slugs and cabbage white butterfly may be required. Keep plants cool when the weather warms, shade if necessary.
Flowering starts when there are about 7 to 8 leaves on the plant, the whole plants are harvested as the first flower buds begin to open, usually between 30 to 50 days after sowing dependent on temperatures. Harvest by cutting with a sharp knife at the base.
Whole young leaves, stems and flowering shoots can be used in making salads. Choi Sum can be lightly boil, steam, stir-fry, combined with other greens and used in soups.
Simply wash the greens thoroughly and split the larger stems in half, lengthwise and blanche in some chicken broth just long enough to soften the stem, but still leave some bite, say a minute or so. Drain and add some oyster sauce and toss. Serve hot or warm. A little drizzle of sesame oil works as well. So simple, yet so satisfying.
Although best eaten when fresh, Choy Sum can be stored in the refrigerator for 5 to 7 days. Place in a plastic bag lined with a paper towel to absorb any excess moisture.
Choy Sum, Brassica chinensis var. parachinensis (or Brassica rapa var. parachinensis) is native to mainland China and is one of the most important leafy vegetables in South China. At least 30 distinct varieties are cultivated there, specifically selected based upon the number of days it takes each variety to mature.
In China, many vegetables are often called by the plant portions being used for cooking. ‘Choy Sum’ in Chinese, means the central stems and flower tips of vegetable. If directly translated Choy Sum means literally ‘vegetable heart’ in Cantonese.
Choy Sum can be spelt Choi Sum and is commonly known as Chinese flowering cabbage, Yi Choy, Yu Toy, and False Pak Choi.
In Asia this vegetable is known as:
China: Tsoi sum and cai xin
Thailand: Pakauyai or pakaukeo
Vietnam: Cai ngot
- Additional Information
Packet Size 1 gram Average Seed Count 425 Seeds Seed Form Natural Seeds per gram 425 seeds per gram Common Name Choi Sum, Yi Choy, Flowering Cabbage Other Common Names Hon Tsai Tai Family Brassicaceae Genus Brassica Species chinensis var. parachinensis Cultivar Gunsho - also spelt 'Guncho' Synonym Brassica rapa var. parachinensis Hardiness Hardy Annual Height 30cm (12in) Spread 35cm (14in) Position Full sun in cool regions and in partial shade in warm regions. Time to Sow Sow in spring through to autumn. Time to Harvest 80 days to maturity.