Common Name: Glutinous Yam

General Information

Dioscorea japonica is a perennial climbing plant growing from a large, vertical, cylindrical tuberous rootstock that can be up to 100cm long and 30mm in diameter. One to several twining shoots up to 300cm long are produced, these shoots twine to the right[].
The plant is harvested from the wild for local use as a food and medicine

Known Hazards

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

Botanical References

,

Range

E. Asia - northeast India, southern China, Korea, Japan.

Habitat

Wooded foothills[]. Mixed forests and margins, scrub forests, herb communities, mountain slopes, valleys, along rivers and streams, roadsides; at elevations from 100 - 1,200 metres[].

Properties

Edibility Rating
Medicinal Rating
Habit	Perennial Climber
Height	0.00 m
Self-fertile	No
Cultivation Status	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[].
A dioecious species - both male and female forms must be grown if fruit and seed are required.

Edible Uses

Tuber - cooked[, , ]. A very pleasant mild flavour with a floury texture, the roots can be eaten as a potato substitute[]. The starch can be used as a binding agent for other foods[]. Roots contain about 1.9% protein, 20% carbohydrate, 0.1% fat and 1% ash[].

Leaf tips - cooked[].

Tubercles - cooked[].

Medicinal

The tubers are prescribed in the treatment of diarrhoea, enteritis, enuresis and spermatorrhoea[]. They are also dried and cut into shavings then used as a tonic[].

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[].

Other Uses

None known

Propagation

Seed - sow early spring to mid spring in a sunny position in a warm greenhouse 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 in a greenhouse for their first year. Plant out in late spring as the plant comes into new growth.
Basal stem cuttings in the summer[].
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 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[].