Dioscorea japonica Another variety of “Wild Mountain Yam”. Very similar to the Chinese Yam, except this variety produces tubers that grow more like sweet potatoes. Instead of growing straight down like the Chinese Yam, these grow more horizontally and are somewhat easier to dig. They also can produce multiple tubers. This variety may be what is known in Japan as ichoimo (5 fingers)
Once you receive the bulbils, I would plant in 3″ or 4″ pots with regular potting mix. Plant at a depth of 1/4″. Once plants begin vining they can be set out into garden. The bulbils can also be planted directly into garden soil but I have better success starting as a transplant. Space plants 2 foot apart. I would also highly recommend planting into a tall raised bed. These tubers can get very large and are quite fragile. Having loose soil around the tubers makes digging easy. Tubers should be dug 2nd year for best size and quality. This plant also requires some type of trellis to grow on. In the fall, the vines will be covered with tiny bulbils which can be harvested and replanted.
These are excellent sliced thinly and fried like a potato chip. They are also excellent baked and roasted. In Japan, mountain yam (Jinenjo) is most commonly eaten raw as “tororo”. The yam is peeled and then grated into a miso broth and served over cooked rice or barley. They can also be stored over the winter like an Irish potato. This is truly one of the few perennial staple crops for the north and worthy of greater attention!
*As a side note. In ancient Japan, women were forbidden to eat jinenjo, for fear they would become too powerful and acquire too much strength!