Clover is the common name attributed to the genus Trifolium, which includes about 250-300 species of legumes. Clover species are cultivated for fodder purposes, to improve soil quality (they form knotweed, which enriches the soil with nitrogen), for decorative purposes (can replace turf), for medicinal purposes, or as a melliferous plant. The most cultivated clover species are red clover (Trifolium pratense) and white clover (Trifolium repens). Species in the genus Trifolium are annual, biennial, or perennial plants. A forage crop of clover is viable for 3-4 years.