Choi sum is one of the most popular vegetables in Chinese cuisine, also widely grown and used in Europe. It is also known as Chinese flowering cabbage.
Choi sum plant has yellow flowers on slightly fleshy stems 0.5 to 1,5 cm in diameter and 15 to 30 cm long, depending on variety. The height of the plant varies from 20 – 40 cm. Leaves are light or dark green and are oval or egg-shaped with slightly serrated margins. The whole plant is edible.
Choi sum is a cool season crop that prefers uniform conditions, good moisture levels and reasonable sunlight. It can be grown all year round when seasons are not too extreme, but higher temperatures may result in thinner, tougher and less sweet shoots or may lead to bolting.
The optimum temperature for growing can be between 15°-25°C.
In China, choi sum varieties are classified by the number of days from sowing to harvest. Available 30, 40, 50, 60, 70, 80 and 90 day varieties.
Choi sum grows in a wide range of soil types, prefers fertile and well-drained soils. The ideal soil pH should be between 7.0 to 7.5.
Choi sum can be grown at plant spacing from 5 – 10 cm and row spacing 10 – 15 cm. In Europe, planting times are from mid to late spring and early autumn. Choi sum is harvested 30-60 days after sowing, 25-30 days after transplanting.
Plants are harvested when the first flower buds begin to open. Stems are cut with a sharp knife at the base.
Choi sum is stored 0-5oC at a relative humidity of 95 to 100%.