Dioscorea colocasiifolia Dalz. Non Pax
Dioscorea sativa Beatson.
Common Name: Yellow Yam
Yellow yam is a climbing perennial plant, producing annual stems 10 - 12 metres from a tuberous rootstock[
]. These stems scramble over the ground, or twine into the surrounding vegetation[
The root is a widely eaten staple food in much of Africa. The plant was developed from various wild species in western Africa and is now commonly cultivated in the tropical areas of Africa, its cultivation having also spread to the Caribbean, Brazil, the Philippines, Papua New Guinea and some other areas[
Freshly cut tubers can cause skin irritation due to the presence of raphides, which are destroyed when the tubers are cooked[
Western Africa - possibly Dahomey.
Not known in a truly wild situation, having arisen in cultivation.
A plant of the moist, lowland tropics. It grows best in areas where annual daytime temperatures are within the range 20 - 32°c, but can tolerate 12 - 40°c[
]. Plants can be killed at temperatures of 9°c[
]. It prefers a mean annual rainfall in the range 1,200 - 1,900mm, but tolerates 900 - 3,000mm[
]. It prefers a dry season of 2 months or less[
Succeeds in full sun and in moderate shade[
]. For best yields, this species requires a deep, well-drained, sandy loam that is not liable to water-logging[
]. Succeeds in relatively light sandy soils[
], though the soil needs to be very fertile otherwise yields can be low[
]. Prefers a pH in the range 6 - 6.7, tolerating 5.3 - 8[
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[
Requiring a longer growing season than other yams, mature roots are formed in 9 - 12 months from planting[
]. The tuber has a very brief resting period and does not store well[
]. It is in fact best stored, if necessary, in the earth[
The tubers are formed near the surface of the soil[
] and can be carefully removed from the growing plant without disturbing it, allowing the plant to continue cropping for up to three years[
]. The tubers can be dug up as required and a common practice is to expose one side of the tuber and to cut away the distal part for consumption leaving the upper part to regenerate; hence the name 'cut-and-come-again'[
]. This practice may be repeated for upward of three years[
Yields of 30 tonnes per hectare have been obtained in the Caribbean[
There are some named varieties[
Although occasionally monoecious, the plant is usually dioecious, therefore both male and female forms need to be grown if seed is required[
Root - cooked in various ways and eaten as a vegetable[
]. A palatable flavour with a dry, mealy flesh[
]. The roots are sometimes dried and milled to produce a flour for storing - this flour is then stirred into boiling water and kneaded to form a paste[
]. The roots have a rough outer skin and a pale yellow flesh[
].The roots are up to 3kg in weight[
]. The roots can contain up to 91% carbohydrate, the highest for any yam[
]. Protein content is low, about 2.5%[
A tea is made from the leaves[
Seed - rarely produced, they are not normally used to propagate this species.
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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