Key Points of Choi Sum Cultivation Techniques and Field Management Methods Explained

Choi sum (flowering Chinese cabbage, Brassica rapa subsp. chinensis var. parachinensis) is an annual or biennial herbaceous plant of the genus Brassica in the mustard family (Brassicaceae). Its tender flower stalks and leaves are the main edible parts, with a crisp, tender and mildly sweet taste, and it is a common leafy vegetable popular in South China. It has a short growth cycle and strong adaptability, and in regions with suitable climate, multiple crops can be arranged in a single year, being especially common in autumn and winter.

Divided by growth period, choi sum can be broadly grouped into three types: early-maturing, mid-maturing and late-maturing. Early-maturing varieties have relatively good heat tolerance and are mostly planted in summer and autumn; late-maturing varieties have strong cold tolerance and are suitable for overwintering or early spring cultivation, and the flower stalks they produce are thick and plump, with better quality. Growers can choose suitable varieties according to the local climate and market timing.

For planting choi sum, it is best to choose loose, fertile sandy loam with convenient drainage and irrigation, and to apply sufficient decomposed organic fertilizer as a base fertilizer when preparing the land. In production, direct seeding is mostly used; after sowing, keep the soil moist to aid emergence, and after emergence, thin and set the seedlings in time to avoid crowding and spindly growth of the seedlings. Choi sum needs a lot of water during its growth period, so it should be watered frequently in small amounts, keeping the ground alternately dry and moist; topdressing should be mainly nitrogen fertilizer, applied lightly and frequently, which can promote thick flower stalks and glossy green leaves. In high-temperature seasons, pay attention to shading and cooling; in low-temperature seasons, covering for insulation can be adopted to reduce cold damage and the problem of premature bolting.

When the main stalk grows level with the leaves and the flower buds at the tip first begin to open, it can be harvested; at this time the flower stalk is the most tender and of the best quality. Common insect pests of choi sum include aphids and cabbage caterpillars, while diseases are mostly downy mildew and soft rot, which can be prevented through rational crop rotation, timely drainage and clearing away diseased and residual plants. After harvesting the main stalk, strengthening fertilizer and water management can also promote the sprouting of side stalks, extend the harvest period and increase overall returns.