The Japanese Mountain Yam (Dioscorea Japonica) or Jinenjo Yam, is also known as “Yamaimo” in Japan, as well as the “East Asian Mountain Yam” elsewhere. The yam can often be mistaken and mislabeled as the Chinese Yam as they are very similar visually. It is native to Japan, China, Taiwan, Korea, and Northern India. Due to its sparse and wide spread nativity throughout southern Asia, there have been 4 accepted forms of subspecies of Dioscorea Japonica which include:
- Dioscorea japonica var. japonica
- Dioscorea japonica var. nagarum
- Dioscorea japonica var. oldhamii
- Dioscorea japonica var. pilifera
Jinenjo is a hearty and productive perennial root crop that can be grown in full sun to partial shade and between heartiness zones 4-10. Because of this wide range of heartiness, the yam can be grown in a vast amount of climates, making very accessible to farmers all around the world. Historically, people have thought that yams were only able to be grown in tropical climates, but the Japanese Mountain Yam due to its heartiness can be grown all over North America and even in the Cascadia regions close to home.
The tubers of the plant grow at the base of the vines like a cluster of sweet potatoes. The vines will grow upwards of 4m tall. It also grows small tubers on the vines that look similar to air potatoes. These are often suitably used for seeding the plant. If the plant is desired to be maintained as a perennial, at least one tuber must be left in the ground, or cut the top third off one or two tubers and replant them.
The plant is comparable in visuals to that of a taro root, making it easy to describe to those who may not be familiar to the appearance of the plant. The plant itself has edible roots which are the plant tubers which are most commonly consumed. The air potato-like shoots are also edible but not consumed nearly as much due to the inferior size of the fruits.
Interestingly enough, the Japanese Mountain Yam is the only known yam to be consumed raw. Traditionally in Japan, it is often served cut or shaven julienne-style raw and either served with an egg on top, or with various other sauces including soy sauce or wasabi and eaten as a light salad/appetizer. Also has been eaten with steamed eel and diced cucumber.
In terms of its medicinal uses, many studies have shown that it could be a natural antioxidant and anti-inflammatory agent, and may also be beneficial for intestinal health and oxidation prevention.
Jacke, D., & Toensmeier, E. (2005). Edible Forest Gardens (Vol. 1&2). White River Junction, VT: Chelsea Green Publ.
Toensmeier, E. (2007). Perennial Vegetables: From Artichokes to Zuiki Taro, A Gardener’s Guide to Over 100 Delicious and Easy to Grow Edibles. Chelsea Green Publishing.