These plants were introduced as ornamentals but have taken over natural habitats all over the eastern United States. It forms heavy vines which girdle, strangle, and kill trees and shrubs. It disperses mainly though runners.
This deciduous woody vine is identified by its fragrant clusters of drooping lavender flowers. The flowers bloom in spring. There is also a native variety which produces similar flowers, the native variety, however, will not climb or spread as aggressively. Infestations of wisteria are very likely the non-native varieties. The leaves of the exotic wisteria species are compound, with 7 - 13 leaflets per leaf (up to 12" long). The leaflets (3" long) are wavy and lance-shaped. The exotic wisteria also has velvety seed pods (4 - 6" long) and the native wisteria has smooth pods.
Fact Sheet: Japanese Wisteria
Photo credits (left to right): Chris Evans, River to River CWMA, Bugwood.org; James H. Miller, USDA Forest Service, Bugwood.org