When the flower stem of lettuce expands, it provides sufficient nutrients.

Lettuce Compositae, lettuce, annual or biennial herbs. Lettuce can be divided into two types: leaf and stem. Leaf lettuce is also known as lettuce, stem lettuce is also known as lettuce, asparagus. The flesh of lettuce is tender, and the stem can be eaten raw, salted, fried, dried or pickled. Lettuce mainly eats leaves or leaf balls, lettuce stems and leaves contain lettuce, bitter taste, high temperature and drought bitter taste, can enhance gastric juice, stimulate digestion, increase appetite, and have analgesic and hypnotic effects. Cultivation techniques. 1. Sowing: sow seeds evenly, press once gently after sowing, suppress with pedals, irrigate cover dung, and keep the bed soil moist before emergence. The seedlings emerged 7-10 days after sowing, and the distance between seedlings was 2-3 cm after a week of fertilizer and water management. Stem lettuce is sown in early autumn, but it is difficult to cultivate at high temperature, so low temperature treatment should be adopted. After soaking the seeds in cold water for 6 hours, put them in the lower layer of the household refrigerator and keep them at 5-8 degrees. After 2-3 days, 60% of the seeds can be sown when they are white. The growth period of leaf lettuce is shorter than that of stem lettuce, and it can be cultivated in the rest of the time except that it is difficult to cultivate in extreme summer and cold. two。 Planting: the seedling age of lettuce is 30-50 days, and it is planted with 4-5 leaves. Spring lettuce is generally planted in November, but it is not suitable for planting between December and January because the soil temperature is too low and the temperature is too low. Late sowing seedlings can be planted in the first ten days of February. The distance between the row and plant of the general early-maturing variety is 16-20 cm square, and that of the late-maturing variety is 26-33 cm square. 3. Field management: spring lettuce has a long growing period, low temperature after planting, slow seedling growth, and less absorption and utilization of water and nutrients before the year. Generally, water is irrigated after planting, fertilizer is applied after survival, and heavy fertilizer is applied to prevent freezing before freezing. After 10 years, topdressing should be applied to promote the growth of foliage. When the flower stem begins to expand, it is provided with sufficient nutrients and water to facilitate the formation of fat tender stems. Autumn lettuce is easy to bolt under the condition of high temperature drying and lack of fertilizer. Therefore, in management, water and fertilizer should be diligent, and water and fertilizer should be uniform to promote the rapid sturdiness and fatness of tender stems.