Chinese yam (Dioscorea polystachya), also called cinnamon-vine, is a species of flowering plant in the yam family. This perennial climbing vine native to China now grows throughout East Asia (Japan, Korea, Kuril Islands, Vietnam). It is believed to have been introduced to Japan in the 17th century or earlier. Introduced to the United States as early as the 19th century for culinary and cultural uses, it is now considered an invasive plant species. The plant was introduced to Europe in the 19th century during the European Potato Failure, where cultivation continues to this day for the Asian food market. The edible tubers, often called nagaimo or Chinese-potato, are cultivated largely in Asia and sometimes used in alternative medicine. This species of yam is unique as the tubers can be eaten raw.
The botanical names Dioscorea opposita and Dioscorea oppositifolia have been consistently misapplied to Chinese yam. The name D. opposita is now an accepted synonym of D. oppositifolia. Botanical works that point out the error may list, e.g., Dioscorea opposita auct. as a synonym of D. polystachya. Furthermore, neither D. oppositifolia nor the prior D. opposita have been found growing in North America and have no historical range in China or East Asia, this grouping is native only to the subcontinent of India and should not be confused with Dioscorea polystachya.
Dioscorea polystachya vines typically grow 3–5 meters long, but can be longer. They twine clockwise. The leaves are up to 11 centimeters long and wide. They are lobed at the base and larger ones may have lobed edges. The arrangement is variable; they may be alternately or oppositely arranged or borne in whorls. In the leaf axils appear warty rounded bulbils under 2 centimeters long. The bulbils are sometimes informally referred to as "yam berries" or "yamberries". 
New plants sprout from the bulbils or parts of them.
The flowers of Chinese yam are cinnamon-scented.
The plant produces one or more spindle-shaped or cylindrical tubers. The largest may weigh 10 pounds and grow one meter underground. Dioscorea polystachya is more tolerant to frost and cooler climates than other yams, which is attributed to its successful introductions and establishment on many continents.
In Chinese it is known as huáishān (怀(淮)山), shānyào (山药, 山藥) (lit. "mountain medicine."), or huáishānyào (怀(淮)山药, 怀(淮)山藥)(lit. "mountain medicine from Huai", i.e. Huai Qing Fu (怀庆俯) region). Rarely, also referred to as shǔyù (薯蕷). The yam bulbils are referred to as shanyao dou 山药豆, i.e. "yam beans", or shanyao dan 山药蛋 ("yam eggs").
In Japanese, it is known as nagaimo (lit. 'long yam'; kanji: 長芋). Furthermore, nagaimo is classified into ichōimo (lit. 'ginkgo-leaf yam'; kanji: 銀杏芋), or yamatoimo (lit. Yamato yam; kanji: 大和芋), depending on root shapes. In Japan, this species is sometimes mistakenly called Japanese mountain yam, which refers to the native Dioscorea japonica.
In Vietnam, the yam is called củ mài or khoai mài. When this yam is processed to become a medicine, the yam is called hoài sơn or tỳ giải.
In the Ilocano of the northern Philippines it is called tuge.
In Latin American countries it's known as white name or white ñame.
In Manipuri it is called as "Ha".
In alternative medicineEdit
Creams and dietary supplements made from the related Dioscorea villosa are claimed to contain human hormones and promoted as a medicine for a variety of purposes, including cancer prevention and the treatment of Crohn's disease and whooping cough. However, according to the American Cancer Society, the claims are false and there is no evidence to support these substances being either safe or effective. Huáishān has also been used in traditional Chinese medicine.
As an invasive speciesEdit
Dioscorea polystachya was introduced to the United States in the 1800s when it was planted as an ornamental or food crop. It and other introduced yam species now grow wild there. It is troublesome in Great Smoky Mountains National Park, where its range is "rapidly expanding". It is most prevalent in moist habitat types. It is more tolerant of frost than other yams and can occur in temperate climates as far north as New York.
The tubers of D. polystachya can be eaten raw, while other yams must be cooked before consumption (due to harmful substances in the raw state). In Japanese cuisine, it is eaten raw and grated, after only a relatively minimal preparation: the whole tubers are briefly soaked in a vinegar-water solution, to neutralize irritant oxalate crystals found in their skin. The raw vegetable is starchy and bland, mucilaginous when grated, and may be eaten plain as a side dish, or added to noodles.
It is used in the Japanese noodle dish tororo udon/soba and as a binding agent in the batter of okonomiyaki. The grated yam is known as tororo (in Japanese). In tororo udon/soba, the tororo is mixed with other ingredients that typically include tsuyu broth (dashi), wasabi, and green onions.
Growing Chinese yamEdit
The Huáishān growing cycle spans approximately one year, and should be planted between winter and spring. The traditional methods growing it are: using smaller tubers, top cut of bigger tubers or through cuttings of branches. The first two methods can produce 20 cm (7.8 in) long tubers and above. The latter produces smaller tubers (10 cm or 4 in) that are usually replanted for the next year.
Between 7 and 9 months of replanting huáishān seedlings, their leaves start to get dry (a common fact in plants that grow tubers): that indicates that it's time to harvest. In home gardens generally only what will be consumed is harvested, with the rest left in the pot in moist soil.
- "Dioscorea polystachya". World Checklist of Selected Plant Families (WCSP). Royal Botanic Gardens, Kew. Retrieved 1 February 2014.
- "Dioscorea polystachya". Germplasm Resources Information Network (GRIN). Agricultural Research Service (ARS), United States Department of Agriculture (USDA). Retrieved 17 December 2017.
- Watts, D. C. (2007-05-02). Dictionary of Plant Lore. Academic Press. ISBN 9780080546025.
- Chinese yam at the Encyclopedia of Life
- "Dioscorea polystachya Turczaninow". TSUYUZAKI Shiro. Hokkaido University. Retrieved 1 February 2016.
- "Forest Invasive Plants of the Northeastern Area - Chinese Yam or Cinnamon Vine". na.fs.fed.us. Retrieved 2016-02-01.
- Invasive Plant Atlas of the United States, entry for Dioscorea polystachya
- Gucker, Corey L. (2009). "Dioscorea spp". Fire Effects Information System (FEIS). US Department of Agriculture (USDA), Forest Service (USFS), Rocky Mountain Research Station, Fire Sciences Laboratory – via https://www.feis-crs.org/feis/.
- "Chinese Yam (Dioscorea Opposita)". www.onlyfoods.net. Retrieved 2016-02-01.
- Raz, Lauren (2002). "Dioscorea polystachya". In Flora of North America Editorial Committee. Flora of North America North of Mexico (FNA). 26. New York and Oxford – via eFloras.org, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
- Ting, Chih-chi; Gilbert, Michael G. "Dioscorea polystachya". Flora of China. 24 – via eFloras.org, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
- "Dioscorea oppositifolia". World Checklist of Selected Plant Families (WCSP). Royal Botanic Gardens, Kew. Retrieved 12 August 2014.
- Christopher, Thomas, ed. (2011), The New American Landscape: Leading Voices on the Future of Sustainable Gardening, Timber Press, p. 121, ISBN 1604691867
- Toensmeier, Eric; Bates, Jonathan (2013), Paradise Lot: Two Plant Geeks, One-Tenth of an Acre, and the Making of an Edible Garden Oasis in the City, Chelsea Green Publishing, pp. 185–188, ISBN 1603583998
- Originated from Jiaozuo (焦作), previously known as "Huai Qing Fu (怀庆俯)" "四大怀药的历史文化渊源".
- "Wild Yam". American Cancer Society. November 2008. Retrieved 21 September 2013.
- Xu, Dermatology in Traditional Chinese Medicine, 2004
- "Dioscorea polystachya". County-level distribution map from the North American Plant Atlas (NAPA). Biota of North America Program (BONAP). 2014.
- Takeguma, Massahiro. "Growing Nagaimo". Retrieved 26 July 2013.
|Wikimedia Commons has media related to Chinese yam.|
- Walck, J. L., et al. (2010). Understanding the germination of bulbils from an ecological perspective: a case study on Chinese yam (Dioscorea polystachya). Ann Bot 106 (6): 945-955.
- Plants for a Future. Dioscorea batatas
- Go Botany, New England Wildflower Society
- Center for Invasive Species and Ecosystem Health, Chinese yam Dioscorea polystachya Turcz.