Dioscorea esculenta aka Chinese Yam

Dioscorea esculenta, the lesser yam or potato yam, belongs to the yam family, Dioscoreaceae. It is native to tropical Asia. Growers raise it as a food crop across tropical Asia and the Pacific. Its cultivation in China dates back more than 1,700 years. This perennial climber grows from a tuberous rootstock. Each year, it sends out stems that trail or twine through nearby plants.

Stems reach about 10 feet [3 metres] long. Another account gives a height of 8 feet [2.4 metres]. Reported spread ranges from 1.6 to 6 feet [0.5–1.8 metres]. The plant has spines, and its leaves are often heart-shaped. Its underground tubers are oval, with white or yellow flesh. A plant can yield five to twenty tubers. These reach about 0.7 feet [0.2 metres] long. Most weigh 250–1,000 grams, though some reach 3,000 grams.

This yam grows in tropical lowlands, in both drier and wetter areas. It occurs up to about 2,950 feet [900 metres] above sea level. Warm days suit it best, with a preferred range of 28–32°C. Temperatures of 9°C or less can kill it. PFAF lists USDA zones 8–12, but this conflicts with the stated cold limit. It favours a clear dry season lasting two to five months. It can also grow in drier climates with rain spread through the year.

Full sun or light shade suits this species. It prefers moist soil, but needs good drainage. Deep sandy loam gives the best tuber yields. Avoid sites where water collects around the roots. It can also grow in poor, gravelly soil enriched with organic matter. Its preferred soil pH is 5.5–6.5, though it tolerates a wider range. Growers tend to use tuber pieces rather than seed. They let cut surfaces dry in the sun before planting. This helps wounds heal and lowers the risk of fungal infection.

The tubers serve as a cooked vegetable and a staple food. Their sweet taste recalls chestnuts or sweet potatoes. Food production is the main garden use described for this plant. PFAF also includes it among plants for food forests. That source warns that some plant parts are poisonous if eaten. This warning does not identify the parts, so it does not establish whole-plant safety. PFAF lists no known medicinal or other uses.