Frost's Descent, the 18th of the 24 solar terms and the last solar term of autumn, begins around October 23 or 24 on the Gregorian calendar each year. The Collected Explanations of the Seventy-Two Pentads in the Monthly Ordinances says: "In the middle of ninth month, the air becomes cold and congeals; dew condenses into frost." The arrival of Frost's Descent means that the weather is getting colder and the first frost appears; cold-sensitive crops have already been harvested or are about to stop growing, and grasses and trees begin to turn yellow and shed leaves, presenting a scene of late autumn. For farmers, Frost's Descent is not merely a climatic marker; it is an urgent summons to farm work.
During Frost's Descent, the whole country enters a busy stage of autumn harvesting, autumn plowing, autumn sowing, and autumn planting, but the focus of farm work differs between the north and the south. In most parts of the north, the autumn harvest is already winding down. Even cold-tolerant scallions can no longer grow. In North China, Chinese cabbage is about to be harvested, and farmers need to strengthen late-stage management to ensure a high and abundant yield. At the same time, because the north has relatively less light and heat resources than the south, Frost's Descent is a critical window for seizing the farming season and sowing winter wheat in time. On the Chengdu Plain, there is an interval of at least one or two months between the rice harvest and wheat sowing, giving farmers enough time to dig drainage ditches, plow and sun-dry the fields, and carry out rotary tillage and land preparation, so that wheat can be sown on schedule after Frost's Descent. In the south, it is the busy "three autumns" season-harvesting single-season hybrid rice and late rice, sowing early-stubble wheat, transplanting early-stubble rapeseed, picking cotton, pulling up cotton stalks, plowing and preparing the land, and also preventing pests and diseases. In fields after harvest, straw and stubble should be collected promptly, because they harbor many overwintering insect eggs and pathogens; clearing straw from the fields and deep-plowing the soil can effectively reduce the occurrence of pests and diseases the following year. For wheat fields where seedlings have already emerged, soil moisture should be preserved in a timely manner; in areas that have not yet been sown, sowing must be carried out promptly. Cold-tolerant vegetables such as celery and Chinese greens need strengthened watering and pest control, while warm-season crops in greenhouses, such as tomatoes, cucumbers, and eggplants, need better insulation and cold protection, timely watering, and prompt harvesting.
Although Frost's Descent has "frost" in its name, frost itself is not entirely harmful. Through long-term production practice, farmers have also recognized frost's "merits": when water vapor condenses, it releases latent heat, which can slow the drop in temperature and reduce the degree of freezing of plants; when frost melts, it absorbs a large amount of heat, which helps frozen plants gradually recover. Frost can also improve the quality of winter vegetables. For example, frosted radishes taste sweeter, because low temperatures promote material transformation and sugar accumulation in plants.
Frost's Descent is the finale of autumn and a key juncture in the rhythm of agricultural work. The agricultural customs of Frost's Descent are both a reward for a year of hard work and a prelude to accumulating strength for the next spring's plowing. As the ancients said, "At Frost's Descent, all crafts rest"; yet amid the rest, new cultivation is quietly brewing.
