Dioscorea cayennensis rotundata
Dioscorea occidentalis Kunth
Dioscorea rotundata Poir.
Common Name: White Yam
White yam is a perennial climbing plant with annual stems that are often prickly and can grow up to 12 metres long. These stems, which twine to the right, scramble over the ground, or twine into the surrounding vegetation[
The plant was developed by selection in Western Africa from wild species and is not known in a truly wild state[
]. It is widely cultivated in tropical areas, especially western Africa, South America and the Caribbean, for its edible root[
Tropical West Africa - Senegal to Nigeria.
Not known in a truly wild state.
A plant of the moist tropics. It grows best in areas where annual daytime temperatures are within the range 25 - 32°c, but can tolerate 15 - 38°c[
]. It can be killed by temperatures of 9°c or lower[
]. It prefers a mean annual rainfall in the range 1,000 - 1,500mm, but tolerates 800 - 3,000mm[
]. Prefers a well-defined dry season of 4 - 6 months[
For best yields, yams generally require a deep, well-drained, sandy loam that is not liable to water-logging[
]. This species is more tolerant of heavier soils with an appreciable clay content[
]. Prefers a pH in the range 6.4 - 6.7, tolerating 5.8 - 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[
].Plants take 7 - 9 months to reach maturity and yields in the range of 16 - 20 tonnes per hectare have been achieved[
]. The tubers are formed close to the surface of the soil[
]. Early maturing tubers can be carefully removed without damaging the growing plant, allowing a second crop to be produced[
White yams can be stored for longer than other yams, sometimes for several months[
There are many named varieties - those from W. Africa are generally considered to have the best flavour[
A dioecious species, both male and female plants need to be grown if seed is required.
Root - cooked and used as a vegetable[
]. Very palatable, it makes a good fufu[
]. The tubers usually weigh in the region of 2 - 5kg, though they can be up to 10kg[
]. The tuber is about 30 cm or more long and sometimes may reach a great weight, as much as 26 kg being recorded in Nigeria[
Seed - rarely produced, it is not normally used to propagate this species. Seeds are sometimes available for propagation in West Africa[
Cuttings of tubers. Small tubers can be cut into 2 - 4 sections, larger ones into 6 - 8 sections. Each section should have 2 - 3 dormant buds. The cut tuber is often left in the sun for several hours to promote wound healing and reduce the risk of fungal infection[
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