The reason why the variety problem of head lettuce can't be solved is that head lettuce can be divided into three varieties according to the different growth time: early maturity, middle maturity and late maturity. If you choose late-maturing varieties and others choose early-maturing varieties, it is normal that your lettuce does not advance while others' lettuce advances. Therefore, when planting, we should choose suitable varieties according to the local environment and market demand, and ensure the good quality. In normal management, you can see lettuce moving forward. Late-maturing varieties need longer harvest time, so the heading time is longer than other varieties. Improper use of chemical fertilizer. The use of fertilizer is very important in the management of lettuce. Only scientific and reasonable fertilization can maintain the nutritional balance of lettuce in all aspects. Because lettuce is a leafy vegetable, nitrogen fertilizer can make the stems and leaves grow more vigorously and produce more leaves, but nitrogen fertilizer should not be used excessively. If nitrogen fertilizer is used too much, phosphorus and potassium fertilizer will grow, but it will be ignored. Although there are too many leaves, they are not very fat, and there will be no obvious close-up phenomenon among the leaves. Therefore, in the lottery period, the trend of lottery is not obvious.
Insufficient sunshine: Lettuce is the same as cold climate. If it is planted in the open air, it is usually planted in spring, autumn and winter. Even so, lettuce is a comparison of long-day plants, so they must absorb more light during their growth. If there is insufficient light, the leaves will become loose, the balls will become worse, and even no balls will appear. For example, grow lettuce under a big tree. Because the trees are covered with light, lettuce can't absorb enough light. When planted in this environment, the leaves of vegetables will become thinner and it is difficult to gather together. The topic is naturally bad. The temperature is too high. Lettuce is like a cold climate, it is also more hardy, but if the ambient temperature is too high, it is not conducive to its growth. The optimum bulb growth temperature is between 13- 16 degrees. If it exceeds this temperature, it is not conducive to granulation, and the sowing date should be properly controlled. When the temperature is high, some measures can be taken to cool down.
Pests and diseases: During the growth of lettuce, you may encounter some pests, such as ground tigers, crickets and other pests. They will bite the leaves of lettuce, the leaves will be damaged, and the difficulty of moving forward will naturally increase. If the head lettuce is infected with damping-off and soft rot, they will also be damaged during the growth process due to these diseases, or stop growing directly, so that they can't head.