Dioscorea aculeata L.
Dioscorea fasciculata Roxb.
Dioscorea papillaris Blanco
Dioscorea papuana Warb.
Dioscorea sativa L.
Dioscorea spinose Roxb. ex Hook.f.
Dioscorea tiliifolia Kunth
Dioscorea tugui Blanco
Onchus esculentus Lour.
Oncorhiza esculentus (Lour.) Pers.
Common Name: Lesser Yam
Lesser yam is a perennial, climbing plant producing annual stems about 3 metres long from a tuberous rootstock. These stems scramble over the ground, or twine into the surrounding vegetation[
A staple food, it is often cultivated in tropical areas, especially Asia and the Pacific, for its edible root[
]. There is a history of cultivation of this species in China going back over 1,700 years[
Edible species of Dioscorea have opposite leaves whilst poisonous species have alternate leaves[
E. Asia - India, Nepal, Bangladesh, Myanmar, Thailand, Vietnam, Malaysia, Indonesia, Philippines, New Guinea.
A plant of the drier to wet tropical lowlands, where it is found at elevations up to 900 metres. It grows best in areas where annual daytime temperatures are within the range 28 - 32°c, but can tolerate 17 - 45°c[
]. It can be killed by temperatures of 9°c or lower[
]. It prefers a mean annual rainfall in the range 800 - 2,000mm, but tolerates 600 - 8,000mm[
]. Plants like a well-defined dry season of 2 - 5 months[
]. This species will grow in drier climates than other yams, so long as the rainfall is evenly distributed through the year[
Succeeds in full sun and also in light shade[
]. For best yields, this species requires a deep, well-drained, sandy loam that is not liable to water-logging[
]. This species will succeed in poor gravelly soils, especially if enriched with organic matter[
]. Prefers a pH in the range 5.5 - 6.5, tolerating 4.5 - 8.5[
Daylengths of more than 12 hours are preferred during the early growing season since this encourages vegetative growth; daylengths of less than 12 hours towards the end of the growing season will encourage tuber formation and development[
Crops take 7 - 10 months to mature, yields of 7 - 20 tonnes per hectare have been achieved[
There are some named varieties[
Two main forms of this plant are sometimes recognised:-
Var fasciculata (Roxb.)Prain. & Burk. Arose in cultivation and has no spines.
Var spinosa (Roxb.)Prain. & Burk. Is believed by many botanists to be the wild form. It has thorny roots protecting the crown of the rootstock[
]. This is a variable characteristic, however[
The plant rarely produces flowers[
A dioecious species, both male and female plants need to be grown if seed is required.
Root - cooked and used as a vegetable[
]. Sweet and pleasant, with a flavour somewhat like sweet potato or chestnuts[
]. The tubers are oval, up to 20cm long and 6 - 8cm in diameter. Each plant can produce 5 - 20 tubers. The flesh is yellow or white and the average tuber weight may be 250 - 1,000g, though larger ones can weight 3,000g[
Seed - not normally used to propagate this species.
Cuttings of tubers. Pieces of tuber, each weighing around 50 - 80g with dormant buds, are planted in situ 4 - 8cm deep with the stem pointing downwards[
]. The cut tuber is often first left in the sun for several hours to promote wound healing and reduce the risk of fungal infection[
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