Britt Slattery, USFWS

Exotic Wisterias
Chinese (Wisteria sinensis),
Japanese (Wisteria floribunda)

Origin: China (Chinese wisteria) and Japan (Japanese wisteria)

Background
These exotic ornamental wisterias were brought into the United States around 1830. They have been grown extensively in the south and mid-Atlantic and adorn many porches, gazebos, walls gardens and parks. Most infestations in natural areas are a result of escapes from landscape plantings.

Distribution and Ecological Threat
Exotic wisterias displace native herbs, vines, shrubs and trees through shading and girdling. Climbing wisteria vines can kill sizable trees, opening the forest canopy and increasing sunlight to the forest floor, which favors the growth of its numerous seedlings.

Britt Slattery, USFWS

Description and Biology

• Plant: showy, woody, ornamental vines in the pea family (Fabaceae). These vigorous vines can climb trees, apparently limited only by the height of the tree, and have been observed at 65 feet in the canopy. Stems of older plants can grow to 15 inches in diameter. Chinese wisteria vines twine counter-clockwise around the host plant and white-barked Japanese wisteria vines twine clockwise.
• Leaves: compound leaves of both species are about 1 foot in length and alternate along the stem. Chinese wisteria leaves consist of 7 to13 leaflets; Japanese has 13 to 19 leaflets.
• Flowers, fruits and seeds: fragrant, violet to blue-violet flowers, 1/2 to 1 inch long, occur in pendulous clusters that hang from twining stems. Flowering occurs in spring (April-May); fruits are velvety brown seed pods, 4 to 6 inches long, narrowed toward the base, with constrictions in the pods that separate the seeds. American wisteria (Wisteria frutescens), a native to the southeastern U.S., flowers in summer and produces a non-hairy seed pod 2 to 4 inches long.
• Spreads: by seed under favorable conditions and by producing stolons (aboveground stems) that develop roots and shoots at short intervals. Seeds can be carried great distances downstream in water.
• Look-alikes: American wisteria (Wisteria frutescens), trumpet creeper (Campsis radicans).

Prevention and Control
Cutting can be employed for small infestations, or to relieve trees of the weight and damage caused by large twining vines. Use of systemic herbicides (e.g. triclopyr) is probably a more effective method for larger, established infestations.

Native Alternatives

American wisteria (Wisteria frutescens) Fred Nation	trumpet creeper (Campsis radicans) Britt Slattery, USFWS	crossvine (Bignonia capreolata) Britt Slattery, USFWS
pipevine (Aristolochia macrophylla) R. Harrison Wiegand	trumpet honeysuckle (Lonicera sempervirens) Britt Slattery, USFWS

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Publication by USFWS BayScapes Conservation Landscaping Program
http://www.nps.gov/plants/alien/pubs/midatlantic/wist.htm
Last updated: 7 October 2004