Dioscorea tokoro aka Tokoro Mountain Yam

Dioscorea tokoro belongs to the yam family, Dioscoreaceae. This climber lives for years. Its native range runs from southern China to Japan. It grows in zones with a temperate climate. Rhizomes, or stems below ground, keep it alive. In Japan, it grows in lowland thickets and foothills. In China, it grows in mixed woods and bamboo forests. It often grows by ravines there. These sites range from near sea level to about 3,280 feet [1,000 metres].

Its stems wind round the branches of nearby plants. Those plants thus help hold it up. PFAF lists it for sunny woodland edges and garden beds. The species records give no full-grown height or spread. They give few facts about its leaves or fruit. PFAF reports small tubers in the leaf axils. These are the points where leaves join the stem. Growers can use these tubers to raise new plants.

PFAF says it blooms from September to October. Male and female flowers grow on separate plants. Each plant bears flowers of just one sex. Grow both sexes if you need seed. A lone plant cannot fertilise itself. The sources give no flower colour or fruit shape. They give no pest or disease details for this species.

PFAF lists moist soil that drains well as suitable. Its species notes list sand, loam and clay as suitable soils. They also list soils that are mildly acid, neutral or mildly alkaline. Those notes say it cannot grow in shade. But PFAF has few direct facts on how to grow it. Its longer care notes draw on the whole genus. How well it withstands British cold is still unclear. This evidence thus gives no firm hardiness zone. PFAF describes sowing seed in spring in a warm greenhouse. It also lists taking basal cuttings in summer, from the stem base. Plants can be split while dormant, when growth rests. Its seed notes keep young plants under glass for their first year.

Records note food use of the tuber below ground after treatment. PFAF warns that the raw root may be poisonous. It describes soaking or boiling in lye before use. This does not show a safe way to prepare it at home. Do not treat the raw root as food. PFAF also lists past use of root remedies for arthritis and rheumatism. These uses also include prostatitis, cough relief and contraception. These records of use do not prove safety or benefit.