Cajanus is a genus of approximately 37 species of flowering plants in the family Fabaceae (legume family), order Fabales. The genus is distributed primarily across tropical and subtropical regions of Africa, Asia, and Australasia, with its natural range extending from West Africa and Madagascar through the Indian Subcontinent, Indochina, southern China, Taiwan, Malesia, and New Guinea to northern Australia.
Members of the genus are typically shrubby or herbaceous legumes found in seasonally dry tropical open forest, woodland, and grassland, often colonising rocky or disturbed ground. Like most legumes, they form root nodules with nitrogen-fixing bacteria, contributing to soil fertility.
The most significant member economically is Cajanus cajan, the pigeon pea (also called Congo pea), one of the world's major pulse crops. Pigeon pea is cultivated throughout the tropics as a high-protein food source and has been widely introduced to the tropical Americas, additional parts of Africa, and central Asia. Several wild species in the genus are considered important genetic resources for crop improvement of the cultivated pigeon pea.
Cajanus species also have ecological roles as larval food plants for certain Lepidoptera, including Endoclita malabaricus.
Distribution
Cajanus is native to a broad tropical belt spanning West Africa, Madagascar, the Comoros, the Indian Subcontinent, Indochina, southern China and Taiwan, Malesia, New Guinea, and northern Australia. Cajanus cajan and some other species have been widely introduced beyond this range to the tropical Americas, additional African regions, and central Asia.
Ecology
Typical habitats include seasonally dry tropical open forest, woodland, and grassland, often in rocky or disturbed areas. Cajanus species serve as larval host plants for certain Lepidoptera, including Endoclita malabaricus, and, as legumes, support nitrogen-fixing root bacteria that enrich soil.
Cultivation
The pigeon pea (Cajanus cajan) is a major pulse crop grown throughout the tropics and subtropics for its edible seeds. It is valued for drought tolerance, short growing cycle, and high protein content. Wild Cajanus species are cultivated in germplasm collections as relatives of potential use in breeding programs.
Cultural Uses
Pigeon pea (Cajanus cajan) is a staple food across South Asia, East Africa, and the Caribbean, consumed as dal, stew, and rice dishes. The plant's leaves and stems are used as fodder, green manure, and fuelwood in smallholder farming systems.
