Vetch is a large genus in the Fabaceae family, with more than 200 species in the world, distributed intermittently in the northern temperate zone and South America. Mainly distributed in temperate regions of Europe, Asia and North America, and extending to tropical mountains; also intermittently distributed in temperate regions of South America. Originated in the tropics; distribution center in the Mediterranean region. Most are annuals or biennials, with few perennial herbs. The structure and number of chromosomes are variable. Most species have x=7, but there are also 5, 6, 7, 9, 11, etc. According to the second volume of the 42nd volume of "Flora of China" published in 1998, according to Xia Zhendai's research and classification, there are 43 species and 5 varieties of vetch in China, and they are divided into 7 groups (Sect.).

The wild peas cultivated in China are scattered in different groups. The species in the same group have similar morphology and distribution, and are closely related. Mountain vetch, widespread vetch and ribbed vetch were introduced and cultivated from wild species in China, and there are wild types in China. Other species or varieties belonging to the Vetch group (Sect.Cassubicae.Radzh.) together with mountain vetch and ribbed vetch, are closely related, mainly including sericea mountain vetch (V.amoena Fisch.var.sericeaKitag). .), narrow-leaved mountain vetch (V.amoenaFisch.var.oblongifoliaRegel), white-flowered vetch (V.amoenaFisch.ex.DC.f.albifloraP.Y.Fu.et.Y.A.Chen), etc.; belong to the same category as widespread vetch Relative species of the Sect.cracca.S.F.Gray group, mainly including V.craccaL.var.canescensMaxim.ex.Franch.et.Sav.) and V.tenuifoliaRoth wait.