Legumes

Legumes or beans are species of plants in the family Fabaceae (also known as Leguminoseae). The legume family is very large, containing about 12,000 species and 440 genera with species occurring on all of the habitable continents.

The most species-rich groups in the legume family are the milk-vetches (Astragalus spp.) with 2,000 species, indigos (Indigoifera spp.; 500 species), clovers (Trifolium spp.; 300 species), beans (Phaseolus spp.; 200 species), and lupines (Lupinus spp.; 200 species). Although some taxonomists include the closely related species of the families Caesalpinaceae (about 2,200-3,000 species) and Mimosaceae (3,000 species) with the legume family, the greater legume family includes the Fabaceae, Caesalpinaceae, and Mimosaceae.

Some species of legumes are very important as food plants for humans and livestock. Economically legumes are second in agricultural importance only to the cultivated species of the grass family, such as wheat, maize, and rice. Because of the ability of many legume species to utilize nitrogen gas (N₂) in the atmosphere, the foliage and fruits of many legumes are relatively rich in proteins and are important sources of nutrients for humans and other animals. Some species of legumes are also used as ornamental plants in horticulture.