Cowpea, or Black-eyed Pea, a tropical herb with beanlike seeds. Cowpeas have three leaflets. The flowers vary from purple to white. The pods are 5 to 10 inches (12.5 to 25 cm) long and are filled with kidney-shaped or roundish peas. The roots of the cowpea, like those of clover and alfalfa, bear tubercles that store up nitrogen, giving it value as green manure (a plant that is plowed under to fertilize the soil). The cowpea is native to Asia. Formerly, it was widely grown in the southern United States for livestock forage, for hay, and as green manure. Some varieties are used as food in the South.
The cowpea is Vigna unguiculata of the family Leguminosae.