Explain the reason of "immature bolting" of spring cabbage

Spring cabbage is a plant vernalization crop. When the spring cabbage seedlings grow to about 12 leaves, the leaf width is 5 ℃ 7 cm, and the stem base is more than 0.6 cm thick, it is more likely to occur "immature bolting" through vernalization at a low temperature of 12 ℃. In southern Jingfeng No. 1 and Zhonggan No. 11 in the north, they are a strong winter spring cabbage variety, which is generally not easy to occur "immature bolting". It is very popular with vegetable farmers, but when it comes to abnormal climate and improper cultivation management, it is inevitable that "immature bolting" will occur. The reasons are as follows: 1. The relationship with climatic conditions the abnormal climate during and after planting of spring cabbage is also easy to cause "immature bolting". For example, before mid-February 1993, it was warmer than the same period in previous years, so that the growth of seedlings was faster and larger, while the temperature dropped rapidly after mid-February, and there were several times of rain and snow in some areas, resulting in a sustained low temperature. Make it have the conditions to pass the vernalization stage. Therefore, "immature bolting" occurred in spring cabbage in some areas. 2. The climate is the longest in the area related to sowing sooner or later. When it is appropriate to sow seeds, it is necessary to grasp the principle of adjusting measures to local conditions. Sowing seeds according to local habits in normal climate change is generally not easy to occur "immature bolting", but in the case of abnormal weather changes, the earlier the sowing, the overwintering seedling growth is often too large, the development period is also earlier, and the longer the time at low temperature, the greater the probability of "immature bolting". On the contrary, properly sowing, the smaller the overwintering seedlings, wait until the development age, the time at low temperature will be shorter, even if the low temperature will not be a large number of "immature bolting". 3. The relationship between the morning and evening of planting and the management after planting. If spring cabbage is planted too early, especially when the weather is relatively warm, the seedlings grow faster, and it is easy to cause "immature bolting" when it is exposed to low temperature. In overwintering management, the more frequently and frequently the plots are fertilized, the seedlings grow faster and the time to feel low temperature is longer, so the rate of "immature bolting" is also higher. If the seedlings are properly controlled to fertilize, so that the seedlings grow slowly and overwintering before reaching the developmental age, "immature bolting" is not easy to occur.