|Traditional Food Plants of Kenya (National Museum of Kenya, 1999, 288 p.)|
English: potato yam, air potato Giriama: mutokera Luhya (Bukusu): liliakhunyu Luhya: litugu, lirungu Luhya (Maragoli): litugu, liruku Luo: oruka, oroko
Description: A twining dioecious plant. Underground tubers elongate or nearly round and irregular, occasionally absent. Aerial tubers (bulbils) up to 7 cm in diameter, brown, rounded or angular. LEAVES: Alternate with a long petiole, heart-shaped, narrowing towards the apex. FLOWERS: Pink-white, borne on long inflorescences arising from the leaf axils. Male up to 4 per axil and up to 10 cm long. Female up to 3 per axil and up to 30 cm long. FRUIT: A dry capsule to 2 cm long.
Ecology: Tropical Africa (including West Africa), Asia, Pacific islands. Cultivated in western Kenya. High-rainfall lowland and mid-altitude rain forest, wet woodland, swamp and stream edges. Zones I-III.
Uses: FOOD: Aerial tubers roasted or boiled like sweet potatoes (Luhya, Bukusu). Often soaked for about two days in cold water to dissolve out poisonous compounds.
FOOD/MEDICINAL: Boiled tubers peeled and given to children as a cure for measles. Often maintained traditionally in gardens for this purpose (Luhya).
Management: Grown from the mature bulbils. New shoots may also grow from the rootstock. In poor soils it should be planted with manure if possible.
Status: Very rare, probably entirely absent in the wild. The cultivation of this crop in Kenya has declined considerably in recent years.
Remarks: Two varieties are distinguished in Kenya:
· the cultivated var. anthropophagorum (A. Chev.) Summerh. with reduced or absent underground tubers and angular edible aerial tubers
· the wild var. bulbifera has no underground tuber but has rounded aerial tubers; it is reportedly poisonous.
· var. sativa with edible tubers is an Indian variety.
The yams belong to the family Dioscoreaceae, a group of plants which, like the grasses, have one cotyledon (monocotyledons). There are about 600 species in the genus Dioscorea distributed over the tropical and subtropical parts of the world. They are generally dioecious twining climbers, often prickly and arising from a tuberous rootstock. Yams are known for their tubers which may be underground or up on the stem (aerial). The yam tuber is the storage organ for the plant and is the edible part. Many of the species, however, do not have edible tubers.
Yams are cultivated throughout the tropics, especially in South-East Asia, Central and West Africa and in South America. In West Africa they are an integral part of the culture. D. bulbifera, a native species in East Africa and a traditional crop of the Luhya, has long been cultivated in Africa and Asia. Some other species of edible yams cultivated in East Africa include the West African yams (D. cayenensis or yellow Guinea yam) and they are cultivated in Uganda and probably in western Kenya too. D. alata (white yam, originally from India) is also cultivated in Uganda and Tanzania but reportedly not yet in Kenya.