Dioscorea japonica
Common name: Yamaimo, Japanese mountain yam
Dioscorea japonica, a type of yam native to the mountainous regions of Japan, Korea, China, Taiwan, and Assam, belongs in the true yam family (Dioscoreaceae). It thrives in full sun to partial shade and prefers a well-drained site.
D. japonica or yamaimo, which means mountain yam in Japanese, is a climbing vine that can reach three metres (ten feet) tall. It is dioecious and needs cross pollination for seed production. Female vines produce small white or yellow flowers in late summer. These flowers have a cinnamon scent. Male vines grow small tubers on their leaf axils. These small tubers are known as air potatoes. The edible parts of D. japonica include the air potatoes and the fleshy, white speckled tubers buried underground which can be up to ninety centimetres (three feet) long. Yamaimo leaves are similar to sweet potato leaves, heart-shaped with pointed tips.
D. japonica tubers are packed with nutrition, rich in vitamins, minerals, and fibre. Studies have shown that they could be a natural antioxidant and anti-inflamatory. D. japonica is one of the only yams that can be eaten raw. The flavour is described as being similar to jicama. When yamaimo is grated, it takes on a sticky, slimy texture which may be off-putting to some. The Japan Times describes it as being one of the most slimy, slippery foods. For those familiar with Japanese food, yamaimo is an ingredient in okonomiyaki (savoury Japanese pancakes), and kankan (a moist, steamed cake).
Dioscorea japonica can be found in the Japanese Collection (Bed 86).
Text and photos from the Garden by Kumi Sutcliffe. Botanical print from Leiden University via Wikimedia