Common Name: Yam

General Information

Dioscorea deltoidea is a perennial climbing plant growing from a large, spreading, horizontal rhizome around 12 - 15mm thick; it produces vigorous annual stems that twine to the left. The stems scramble over the ground and twine into nearby vegetation[, ].
The plant is sometimes used locally as a medicine, hair wash and food, but it is mainly of importance as a source of the medically active compound diosgenin. It is commonly harvested from the wild for this compound and also sometimes cultivated in countries such as Vietnam and Russia.

Known Hazards

Edible species of Dioscorea have opposite leaves whilst poisonous species have alternate leaves[].

Botanical References

Range

E. Asia - China, northeast India, Nepal, Myanmar, Thailand, Vietnam.

Habitat

Forests and humus-rich soils; at elevations from 1,700 - 2,800 metres in Kashmir[]. Broad-leaved forests and scrub forests; at elevations from 2,000 - 3,100 metres in western China[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Perennial Climber
Height	3.00 m
Self-fertile	No
Cultivation Status	Cultivated, Wild

Cultivation Details

Easily grown in a fertile well-drained soil in a sunny position or light shade[]. Prefers a rich light soil[].
Plants produce tubercles (small tubers that are formed in the leaf axils of the stems), and can be propagated by this means[].
A climbing plant that supports itself by twining around the branches of other plants[].
Dioecious. Both male and female forms must be grown if seed is required.

Edible Uses

Tuber - cooked[, ]. A slightly bitter flavour, it is usually boiled with some wood ash in order to remove the bitterness[]. Some caution is advised. See notes below on other uses of the root and above on toxicity.

Medicinal

The juice of the root tuber is taken in the evening in the treatment of roundworm[]. It is also used to alleviate constipation[].

The roots of most, if not all, members of this genus, contains diosgenin[, ]. This is widely used in modern medicine in order to manufacture progesterone and other steroid drugs. These are used as contraceptives and in the treatment of various disorders of the genitary organs as well as in a host of other diseases such as asthma and arthritis[]. The roots of this species contain an average of 4.8% diosgenin[].

Other Uses

A soap is obtained from the tuber[, ]. This soap is due to the presence of poisonous saponins in the root[, ]. Used for washing shawls and woollen cloth[]. The soap is also used as a body wash to kill lice[, , ].

Propagation

Seed - sow in containersl in a sunny position in a nursery seedbed and only just cover. It germinates in 1 - 3 weeks at 20°c[]. Prick out the seedlings as soon as they are large enough to handle and grow on for their first year. Plant out in late spring as the plant comes into new growth.
Basal stem cuttings in the growing season[].
Division in the dormant season, never when in growth[]. The plant will often produce a number of shoots, the top 5 - 10 cm of the root below each shoot can be potted up to form a new plant whilst the lower part of the root can possibly be eaten[].
Tubercles (baby tubers) are formed in the leaf axils. These are harvested in late summer and early autumn when about the size of a pea and coming away easily from the plant. They should be potted up immediately in individual pots in a greenhouse or cold frame. Plant out in early summer when in active growth[].

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