Its tolerance for sandy soil and low rainfall have made it an important crop in the semiarid regions across Africa and Asia.

A high level of morphological diversity is found within the species with large variations in the size, shape, and structure of the plant.

[13][15] The original subgroups of stenophylla, dekindtiana, and tenuis appear to be common in all taxonomic treatments, while the variations pubescens and protractor were raised to subspecies level by a 1993 characterisation.

[17] 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.

[22] The size and shape of the leaves vary greatly, making this an important feature for classifying and distinguishing cowpea varieties.

[26] New research using molecular markers has suggested that domestication may have instead occurred in East Africa and currently both theories carry equal weight.

[29] The first written references to the cowpea were in 300 BC and they probably reached Central and North America during the slave trade through the 17th to early 19th centuries.

[31] Its nitrogen-fixing ability means that as well as functioning as a sole crop, the cowpea can be effectively intercropped with sorghum, millet, maize, cassava, or cotton.

[33] These characteristics, along with its low fertilisation requirements, make the cowpea an ideal crop for resource-poor farmers living in the Sahel region of West Africa.

[34] The crop is mostly intercropped with pearl millet, and plants are selected that provide both food and fodder value instead of the more specialised varieties.

[37] Temperatures of 60 °C (140 °F) kill the weevil larvae, leading to a recent push to develop cheap forms of solar heating that can be used to treat stored grain.

[38] One of the more recent developments is the use a cheap, reusable double-bagging system (called PICs) that asphyxiates the cowpea weevils.

[39] Insects are a major factor in the low yields of African cowpea crops, and they affect each tissue component and developmental stage of the plant.

[6][41][42][43][44] M. vitrata causes the most damage to the growing cowpea due to their large host range and cosmopolitan distribution.

Genetically modified cowpeas has been developed to express the cry protein from Bacillus thuringiensis, which is toxic to lepidopteran species including the maruca.

[48][49] The weevil generally enters the cowpea pod through holes before harvest and lays eggs on the dry seed.

[53] Cowpea is susceptible to nematode, fungal, bacterial, and virus diseases, which can result in substantial loss in yield.

[56] CPMV is stable and easy to propagate to a high yield, making it useful in vector development and protein expression systems.

[69] Chinese long beans can be eaten raw or cooked, but as they easily become waterlogged are usually sautéed, stir-fried, or deep-fried.

[70] A common snack in Africa is koki or moin-moin, where the cowpeas are mashed into a paste, mixed with spices and steamed in banana leaves.

[74] A popular dish was Hoppin' John, which contained black-eyed peas cooked with rice and seasoned with pork.

Over time, cowpeas became more universally accepted and now Hoppin' John is seen as a traditional Southern dish ritually served on New Year's Day.

[69] The grain is a rich source of folic acid, an important vitamin that helps prevent neural tube defects in unborn babies.

[80] The cowpea has often been referred to as "poor man's meat" due to the high levels of protein found in the seeds and leaves.

[69] Methods such as fermentation, soaking, germination, debranning, and autoclaving are used to combat the antinutritional properties of the cowpea by increasing the bioavailability of nutrients within the crop.