There is a big temperature difference between day and night in this season, so it is necessary to strengthen the protection of coriander, mainly for the northern region, and the south does not need too much protection at present. In the north, the protective measures are plastic greenhouses, which cover parsley, so as to increase the temperature and humidity in the greenhouse, but during the day, the greenhouse should be exposed with an opening to allow air circulation and carbon dioxide. If there are no conditions, you can cover it with straw, but you should open it during the day. This way is afraid of rainy days, and it is not applicable in rainy days.