Dioscorea deltoidea aka Dioscorea

Dioscorea deltoidea is a vine that lives for many years. It belongs to the yam family, Dioscoreaceae. Its native range spans northern Pakistan, south-central China, and Indochina. Records also list eastern Afghanistan, Bhutan, Nepal, and northern India. It grows in forests, scrub, and soil rich in humus. Kashmir records place it at 5,580–9,190 feet [1,700–2,800 metres]. In western China, it reaches 10,170 feet [3,100 metres]. People gather wild plants and grow them too.

The vine grows about 10 feet [3 metres] tall. It grows from a large rhizome, a stem beneath the soil. This stem spreads out flat. It is about 0.04–0.05 feet [0.012–0.015 metres] thick. Strong new stems grow each year and twine to the left. They trail on the ground or climb through nearby plants. The stems use these plants' branches for support. Small tubers called tubercles may grow where leaves meet stems. Growers can use these to raise new plants.

Plants For A Future lists its bloom time as September to October. Each plant has either male or female flowers. To get seeds, growers must grow both sexes together. A lone plant cannot fertilise itself. The sources say little else about the flowers or fruit. Garden records show it in beds and at sunny woodland edges. Its stems need support nearby to climb above the ground.

This plant needs moist soil that drains well. Sources say it can grow in sand, loam, and clay. It accepts soil that is slightly acid or slightly alkaline. Neutral soil suits it too, as do sun and light shade. Plants For A Future is unsure how well it survives British winters. The source doubts it will thrive outside the mildest areas. Growers can raise plants from seeds or summer stem cuttings. They can also divide plants while dormant, when growth stops. They should not divide plants while they grow.

People cook the tuber for food, but the sources urge care. It tastes bitter and has saponins, which are poisonous. Reports describe boiling it with wood ash to make it less bitter. This does not show a safe way to prepare it at home. The tuber also provides soap and washes for use against lice. People have used it to treat roundworm and constipation. Its roots contain diosgenin, a raw material used to make steroid drugs.