The growth period of choy sum is short and it is mainly produced in Hebei, Liaoning, Inner Mongolia, and other regions. However, due to different growing areas and environments, the growth and development time of choy sum can vary. This results in different sowing and harvesting periods. Therefore, when analyzing the cultivation problems of choy sum, it should be considered based on different regions and environments.
1. Cultivation Techniques
1. Planting Season
Choy sum is suitable for spring planting in the northern regions. For example, in Harbin, it can be planted every 15 days from May to June, and can be harvested continuously after June or planted in August and harvested in September. In the southern regions, choy sum is suitable for autumn, winter, and spring planting. For example, in Foshan, it can be directly sown in stages from mid-October to April of the following year, and can be harvested and put on the market from early November to May of the following year. It takes 20-25 days from sowing to harvest. With the help of protected cultivation, except for high-altitude and southern regions, choy sum can be grown all year round.
2. Soil Preparation and Bed Making
Combine plowing and fertilization before sowing. Plow the soil to a depth of 15-20 centimeters, then level the ground and make beds. The bed width should be 80-100 centimeters, with a distance of 30 centimeters between beds. The soil preparation should be meticulous, with no large clods in the beds.
3. Sowing
For open field cultivation, dry sowing can be done before the end of the early spring frost. It can be sown in stages and harvested in stages. Before making the beds, apply sufficient base fertilizer. Sow in 7-9 rows, with a row spacing of 10 centimeters and a sowing depth of 1 centimeter. The sowing amount is 5-10 grams per square meter. It takes 3-6 days for the seedlings to emerge. When the second true leaves appear, thin the seedlings to a spacing of 10 centimeters. The thinned seedlings can be used for consumption.
4. Fertilization and Irrigation
Apply 3-4 kilograms of well-rotted organic fertilizer and 30 grams of ammonium dihydrogen phosphate per square meter before sowing. If the base fertilizer is sufficient, there is no need for additional fertilization. If the base fertilizer is insufficient, apply diluted manure (1:8-10) twice before flowering. The first application should be done when the seedlings have 3 leaves, and the second application should be done when the plants have 5-6 leaves. During the nutrient growth stage, ensure an adequate water supply and avoid water deficiency.
5. Inter-cultivation and Weed Control
After emergence, lightly loosen the soil once at the 2-leaf stage, being careful not to damage the seedlings. After that, regularly cultivate and weed to prevent weed infestation.
6. Pest and Disease Control
The main pests of choy sum are flea beetles, diamondback moths, cabbage moths, cabbage loopers, aphids, leaf miners, red spider mites, and whiteflies. The main diseases are damping-off and lodging during the seedling stage.
7. Harvesting
15-20 days after sowing, when the plants have 6-9 leaves, they can be harvested in their entirety. Alternatively, when the plants reach a height of about 15 centimeters and before flowering, the tender stems and leaves can be harvested. The yield of choy sum is 1-2 kilograms per square meter.
2. Growth and Development
The growth period of choy sum is short. In Harbin, it takes 3-6 days from sowing to emergence, 25-28 days from emergence to flowering, and another 25 days for the seeds to mature. In Foshan, choy sum can be sown in mid-October, emerge after 2 days, flower after 1 month, and the seeds mature after 30 days. The growth and development process of choy sum can be divided into 4 stages.
1. Germination Stage
From sowing to the cotyledons spreading. This stage takes 3-6 days. Under suitable conditions, such as a temperature of 23-25℃, the seedlings can emerge 2 days after sowing. In early spring, when sowing directly in the open field, the emergence is slower due to low temperatures.
2. Seedling Stage
From cotyledons spreading to the formation of 6-8 true leaves and the beginning of stem elongation. This stage takes about 7 days. During the seedling stage, choy sum can be harvested continuously.
3. Bolting Stage
From the start of stem elongation to the beginning of flowering. This stage lasts for about 12-15 days.
4. Flowering and Fruiting Stage
From the start of flowering to seed maturity. Generally, it takes 25-30 days for the seeds to mature after the flowers fade. For choy sum directly sown in the open field in Harbin in early May, the flowering period is in June and the seeds mature in July. In Foshan, for choy sum directly sown in the open field, it takes 30-40 days from sowing to flowering, and the seeds mature after 1 month.
