小白菜品种五月慢，是适于春季栽培的优良品种，冬性极强，因为自然条件下抽薹开花晚，开花授粉时经常遇到高温，种子产量很低。经过多年观察发现不论播期如何提前，其开花日期并不提早。可见五月慢的抽薹开花对低温和长日照有极严格的要求，因此为提高五月慢品种的采种量，必? Chinese cabbage varieties slow in May, is suitable for spring cultivation of fine varieties, winter is extremely strong, because the flowering of late blooming under natural conditions, flowers pollination often encounter high temperatures, the seed yield is very low. After years of observation, it is found that the flowering date is not earlier, no matter how early the sowing date. It can be seen that slow bolting and flowering in May have very strict requirements on low temperature and long sunshine. Therefore, in order to increase the seed collection rate of slow varieties in May,