A climbing vine grown for its large, white-fleshed tuber — the most widely cultivated yam species in West Africa and a cornerstone food crop.
The white yam or white Guinea yam (Dioscorea rotundata, family Dioscoreaceae), now often treated as Dioscorea cayenensis subsp. rotundata, is a perennial vine with a cylindrical, usually spiny stem that twines to the right, and dark, glossy green leaves. It is grown for its tubers, which usually weigh 2 to 5 kg and up to 10 kg on good land; tubers of 20 to 25 kg have been recorded. It is one of the most important yams in the world, grown on a larger area than any other yam species, with many varieties. The tubers are eaten cooked, and in West Africa it is the preferred yam for pounded yam (fufu).
It is native to West Africa and was domesticated there, along the Atlantic coast, probably from the wild Dioscorea praehensilis and possibly through hybridisation with D. abyssinica; when this happened is not known. It is widely grown from Côte d'Ivoire to southern Nigeria, to some extent in East Africa, and in the Caribbean, where it was carried by the slave trade, as well as in Brazil and the Philippines. The tubers take 180 to 300 days to mature, are hard and unpalatable if dug too early, and have a definite dormant period after harvest. The linguist Roger Blench has tentatively reconstructed a Proto-Niger-Congo root, -ku, for this yam.
Sources: PROTA4U database (Plant Resources of Tropical Africa), which compiles records from Royal Botanic Gardens, Kew, the Conservatoire et Jardin botaniques de Genève, FAO EcoCrop and other botanical databases; Wikipedia, "Dioscorea cayenensis subsp. rotundata".
Boiled, pounded into pounded yam, or fried; a major starchy staple across Nigeria.
Yam holds major ceremonial importance at New Yam harvest celebrations across Nigeria; a Tiv-specific protocol was not independently confirmed.
A staked climbing vine requiring fertile soil and a long growing season of 8-10 months.