The cowpea (Vigna unguiculata) is an annualherbaceouslegume from the genus Vigna. Due to its tolerance for sandy soil and low rainfall it is an important crop in the semi-arid regions across Africa and other countries. It requires very few inputs, as the plant's root nodules are able to fix atmospheric nitrogen, making it a valuable crop for resource-poor farmers and well-suited to intercropping with other crops. The whole plant is used as forage for animals, with its use as cattle feed likely responsible for its name.
Four subspecies of cowpea are recognised, of which three are cultivated. There is a high level of morphological diversity found within the species with large variations in the size, shape and structure of the plant. Cowpeas can be erect, semi-erect (trailing) or climbing. The crop is mainly grown for its seeds, which are extremely high in protein, although the leaves and immature seed pods can also be consumed.
Cultivated cowpeas are known by the common names black-eyed pea, southern pea, yardlong bean, catjang, and crowder pea. They were domesticated in Africa and are one of the oldest crops to be farmed. A second domestication event probably occurred in Asia, before they spread into Europe and the Americas. The seeds are usually cooked and made into stews and curries, or ground into flour or paste.
Most cowpeas are grown on the African continent, particularly in Nigeria and Niger which account for 66% of world production. A 1997 estimate suggests that cowpeas are cultivated on 12.5 million hectares (31 million acres), have a worldwide production of 3 million tonnes and are consumed by 200 million people on a daily basis. Insect infestation is a major constraint to the production of cowpea, sometimes causing losses of over 90% loss in yield. The legume pod borer Maruca vitrata is the main pre-harvest pest of the cowpea and the cowpea weevil Callosobruchusmaculatus the main post-harvest pest.
Black-eyed peas, a common name for a cowpea cultivar, are named due to the presence of a distinctive black spot on their hilum.
Vigna unguiculata is a member of the Vigna (peas and beans) genus. Unguiculata is Latin for "with a small claw", which reflects the small stalks on the flower petals. All cultivated cowpeas are found within the universally accepted V. unguiculata subspecies unguiculata classification, which is then commonly divided into four cultivar groups: Unguiculata, Biflora, Sesquipedalis, and Textilis. Some well-known common names for cultivated cowpeas include black-eye pea, southern pea, yardlong bean, catjang, and crowder pea. The classification of the wild relatives within V. unguiculata is more complicated, with over 20 different names having been used and between 3 and 10 subgroups described. The original subgroups of stenophylla, dekindtiana andtenuis appear to be common in all taxonomic treatments, while the variations pubescens and protractor were raised to sub-species level by a 1993 charactisation.
The first written reference of the word 'cowpea' appeared in 1798 in the United States. The name was most likely acquired due to their use as a fodder crop for cows. Black-eyed pea, a common name used for the unguiculata cultivar group, describes the presence of a distinctive black spot at the hilum of the seed. Black-eyed peas were first introduced to the southern states in the United States and some early varieties had peas squashed closely together in their pods, leading to the other common names of southern pea and crowder-pea. Sesquipedalis in Latin means "foot and a half long", and this subspecies which arrived in the United States via Asia is characterised by unusually long pods, leading to the common names of yardlong bean, asparagus bean and Chinese long-bean.
Common names of Vigna unguiculataunguiculata cultivar groups