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Chinese yam leaves and bulbil

Chinese yam (Dioscorea polystachya, D.batatas); Indian yam (D. oppositifolia)

Herbaceous perennial vines with large underground tubers and aerial bulbils. Plants can grow up to 15’ long. It twines counterclockwise and the petioles and stems are purple-red.

Overview

Regulated areas of Chinese yam
These species are Prohibited (Red counties)

Other names for this plant include:

  • Common names: Cinnamon vine, Japanese mountain yam, Korean yam

Ecological threat:

  • Invades stream banks and other riparian areas as well as mesic forests, roadways, fence rows, and drainage ways.
  • Rapid, early growth allows the vine to block out sunlight and shade out native plants. It forms dense mats that can down branches and kill trees. Native ground cover is also displaced and shaded out, unable to penetrate the blanket of vines.
  • Sreads rapidly via aerial bulbils, potentially long distance from parent plant.

Classification in Wisconsin: Prohibited

Species Assessment Groups (SAG) were assembled to recommend a legal classification for each species considered for NR 40. The recommendation for Chinese yam was based upon this literature review developed by the department.

Identification

Leaves: Leaves are generally opposite, but may be alternate in upper nodes. They are spear to oval shaped (or heart shaped), coming to a sharp point. There are 1.5-3” long and up to 1.5” wide with 7-9 parallel leaf veins. Newly emerged leaves are tinted bronze; mature leaves have purple-red leaf edges and petioles.

Flowers: In leaf axils, greenish white flowers bloom on spikes during June-September and produce a cinnamon fragrance.

Fruits & seeds: Aerial bulbils, small potato-like tubers, are produced in leaf axils during June-September. They are spread by gravity, animals and water and can germinate within two weeks of forming. Bulbils are covered with adventitious buds that can produce new plants if damaged.

Roots: Large vertical tubers, up to 3’ long, are produced and can resprout if entire root is not removed.

Similar species: Native wild yam (Dioscorea villosa) twines clockwise and is slightly hairy on the upper surfaces of the leaves. Greenbriars (Smilax spp.) have blue – purple berries and some have thorns. Morning glories (Ipomoea spp.; non-native) and bindweed (Convolvulus arvensis; invasive), as well as the two species previously mentioned, have somewhat similar shaped leaves but lack the aerial bulbils.

Distribution

Known county distribution of Chinese yam
Counties in WI where Chinese yam has been reported (as of July 2011). Both vouchered and unvouchered reports included.

Do you have Chinese yam in your county but it isn't shaded on the map? Send us a report.

Control

Mechanical: In small populations, mow, cut or grub before bulbil production. Do for several years to deplete root reserves.

Chemical: Foliar spray larger populations with glyphosate or triclopyr in July-October when bulbils have not yet ripened.

Photos

View Chinese yam pictures in our photo gallery!

Resources

Sources for content:

  • Czarapata, Elizabeth; Invasive Plants of the Upper Midwest: an illustrated guide to their identification and control. University of Wisconsin Press. 2005. Pg. 127
  • Southeast Exotic Plant Pest Council (SEEPPC). 2003. Southeast Exotic Plant Pest Council Invasive Plant Manual. BugwoodWiki: Chinese Yam - Dioscorea oppositifolia [exit DNR].

Links for More Information

Last revised: Monday December 11 2017