Trifolium or trefoil are common names for plants in the genus Trifolium (from Latin tres “three” + folium “leaf”), which consists of about 300 species of flowering plants in the legume or pea family Fabaceae native to Europe. The genus has a cosmopolitan distribution with the greatest diversity in the temperate northern hemisphere, but many species are also found in South America and Africa, even in the high mountains of the tropics. They are small herbaceous annuals, biennials or short-lived perennials, usually reaching a height of 30 cm. The leaves are three-leafed (rarely four-leafed; see cloverleaf), monoleaf, bileaf, cinquefoil, hexaleaf, septfoil, etc., with stipules adjacent to the petiole and dense heads or spikes of small red, purple, white. , or yellow flowers; the small pods with few seeds are enclosed in the calyx. Other closely related genera often referred to as trefoil are Melilotus (sweet clover) and Medicago (alfalfa or Calvary trefoil).