Any of a group of plants which are mostly annual and perennial legumes with weak viny stems often terminating in tendrils. There are about 150 species in the temperate zones of four continents. The leaves are compound with many leaflets. Vetches are used mainly for green manure, cover crops, hay, and pasture and silage. The seeds are used as concentrate in animal feeds, and some vetches are used as a vegetable for human consumption. Cool temperatures promote best development. Seed is sown in the fall in the Southern United States and in early spring in the Northern states. In general, are vetches more tolerant of acidic soil conditions than are most legume crops, but they have a relatively high requirement for phosphorus. Inoculation of seed with nodule-forming bacteria for symbiotic nitrogen fixation is necessary if vetch has not been previously grown in the field.