Chinese Yam (Dioscorea oppositifolia)
The Chinese yam is a perennial vine native to Asia. The plant was introduced to the United States in the 1800's as a food source and is highly valued in traditional Chinese medicine. Since introduction, the Chinese yam has spread to 16 states, where it suppresses native ecosystems and reduces plant diversity. Despite the aggressive, invasive nature of the Chinese yam, the plant is still widely available as an ornamental. Chinese yam has not yet been found in Michigan; however sightings have been confirmed in Indiana, Illinois and Ohio.
The Chinese yam is a non-woody perennial vine with slender stems that climb and twine around vegetation, growing up to 16 ft. high. The leaves of the Chinese yam are heart or fiddle shaped with parallel veins running the length of the leaf. Leaves typically grow to 1.5-3in. long and up to 1.5in. wide. Vines rarely produce small yellow to white bundles or spikes of flowers in May. The Chinese yam is most easily distinguished by bulbils or air tubers that appear in the axils of the leaves from June through September. The Chinese yam is commonly referred to as the ‘air potato' as these bulbils resemble very small potatoes. New vines sprout from the bulbils which can be carried to new locations via wind, dispersal by animals or through site disturbance. Any part of the bulbil can sprout a new vine. Similar species that are currently found in Michigan include species of Greenbrier (Smilax spp.); Field bindweed (Convolvulus arvensis); and native wild yam (Dioscorea villosa).
The Chinese yam grows rapidly, reproduces easily and is able to establish in many environments including sensitive riparian areas, moist forests and old home sites where vines may have been intentionally planted. Vines die back in the winter, but grow quickly enough to engulf an entire tree in one growing season. If detected early, Chinese yam can be controlled through the use of herbicides, or through long-term mechanical removal efforts.
Preventing the introduction of invasive species is the most effective means to protect our native ecosystems. To learn how to identify and report sightings of Chinese yam visit MISIN. Information on native alternatives to Chinese yam for your garden can be found at Habitat Matters.