Synonyms: Dioscorea batatas，Dioscorea opposita (Thunb.), Dioscorea polystachya (Turcz.), Dioscorea divaricata
Common name: Chinese yam, air potato, Shan yao, Shan yam
Natual Habitat: Valleys and hills in China
Identificationg: Deep-lobed and elongated heart-shaped leaves, stems twine counterclockwise
I took the following pictures in October 2005. The plant was growing near a bamboo forest in a mountainous region near the border of Jiangsu and Zhejiang province. Whether it is planted or wild I do not know. The blooms are tiny and has a very pleasant fragrance. I didn't know at the time what this plant was. Now, from the information I gathered on Dioscorea, it is probably Dioscorea oppositifolia, the so called Chinese Yam or Shan Yao. When I took the picture I thought this could be a very nice garden plant if trained on a trellis. As I later find out, it has spread around the world as a food crop. In China and Japan there are many varieties with different tuber shapes and colors.
Dioscorea oppositifolia is a perennial hardy to zone 5. It can grow to 9 feet tall and 4 feet wide. But I think you have to support it somehow. Not sure whether it can grow that tall without any support. Scented white flowers bloom from September to October. Any single plant has either male or female flowers. So if you want seeds, you have to plant both. However this plant can reproduce either sexually of asexually. It produces axillary tubers, which is called bulbils. A single plant can produce hundreds of bulbils. These bulbils will sprout easily. In some area of the United States, this plant has escaped from cultivation and became an noxious weed, taking over the natural habitat of native flora. (If you are Chinese, you must be thinking: Where is it? I would like to help control this weed by diging out the tuber and eat it:-) If you plant it in your garden, do your best to contain it.
Dioscorea oppositifolia is easy to grow. It likes well-drained soil, sandy loam preferably. Needs a lot of sun, but will take some shade. Average water needs. Propagation is by seed or bulbil. When harvesting the tuber, the lower part could be eaten and the part with sprouts could be planted again.
I like the taste of Chinese Yam. It is the elongated root of this plant, stretching a few feet long. It is widely available in China, Japan, and Korea. It has a very crispy texture if not cooked for too long, otherwise it tasts very much like boiled potato. The flavor is mild and pleasant. I usually stir fry it with some shreded pork, or just by itself. It can also be made into deserts or used in soups. The next picture is a piece of Shan Yao with a funny shape, which I bought in a vegetable market in China.
