Dioscorea oppositifolia
L. (Chinese yam ) |
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Family: Dioscoreaceae (Yam Family) Synonym(s): Dioscorea batatas Duration: Perennial Habit: Vine
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Description: Herbaceous, high climbing vines to 65 feet (20 m) long, infestations covering shrubs and trees. Twining and sprawling stems with long-petioled heart-shaped leaves. Spreading by dangling potato-like tubers (bulbils) at leaf axils and underground tubers. Monocots. History: Introduced from Asia as possible food sources in the 1800s. Ornamentals often spread by unsuspecting gardeners intrigued by the dangling yams. Presently cultivated for medicinal use. Biology & Spread: Dioscorea oppositifolia can reproduce both sexually and asexually. Although it is capable of sexual reproduction, it has not been documented in North America. It does, however, reproduce vigorously asexually, via the production of small potato-like propagules, called bulbils. These bulbils exhibit a relatively low rate of survival in the field (vs. the greenhouse), but plants apparently produce adequate numbers of bulbils to more than compensate for their low rate of survival (Beyerl 2001). Each vine is capable of producing an average 20 bulbils per year (Tu, 2002). Ecological Threat: Dioscorea oppositifolia is a fast growing, twining vine that has escaped from cultivation and has the ability to rapidly invade pristine habitats, especially riparian corridors. It has a swift rate of vegetative growth and a prolific rate of asexual reproduction via bulbils. In North American infested areas, it lowers native species richness and abundance by outcompeting and eliminating native plant species. It does this by quickly outgrowing the native herbs and seedlings, thickly blanketing all adjacent vegetation, and competitively excluding light. It may also weight-down and break branches of large trees and shrubs (similar to kudzu, Pueraria montana). An entire stand of native shrubs may become covered by D. oppositifolia, and it shades and eventually kills the stand. It is also able to completely cover the ground so that all native herbaceous ground cover is excluded. US Habitat: Chinese Yam can survive in a number of different habitats and environmental conditions, but is most commonly found at the edges of rich, mesic bottomland forests, along stream banks and drainageways, and near fencerows (Yayskievych 1999, in Tu, 2002). Initial infestations are generally associated with human-caused disturbances, such as near old home sites and along roadways. From these areas, it can easily spread into nearby riparian swaths and undisturbed habitats. Chinese Yam can tolerate light levels ranging from full sun to full shade, but mostly grows at intermediate light levels along forest edges. Since it is often associated with riparian habitats, it is typically found in silty loam soils, which are typical of alluvial habitats (Beyerl 2001). Distribution
Resembles/Alternatives: Ipomoea spp. - Morning glory (Ipomoea spp.) has a cordate leaf shape but lacks the aerial tubers.
Management: Preventative measures: Tu (2002) states that as with all prolific invaders, the key to the successful control of D. oppositifolia is to prevent new infestations or to control them as soon as possible. In North America, it has a wide range of environmental adaptability and few pests and predators. It has a high degree of asexual reproductive vigor, and is difficult to manage once firmly established. The use of manual and mechanical methods followed by another control technique (for example, periodic herbicide sprays to control for new bulbil recruitment and root sprouts) for several years should be accompanied by active restoration efforts to obtain desired results.
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Text References
Data Source Last Updated: 2024-01-29 by ARMO, TISI |
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