Wisteria floribunda (Willd.) DC.
Rehsonia floribunda (Willd.) Stritch
Rank: Lesser Threat
Plant Type: Vine
Wisteria is a woody vine that can grow up to 70 feet (20 m) in tall canopy trees.
The vine stems can get up to 10 inches (25 cm) in diameter. Branching is alternate. Older bark of Chinese wisteria is tight and dark gray with light colored lenticles (dots). Japanese wisteria bark is white.
Twigs are densely short hairy, and twine counter-clockwise in Chinese wisteria. Japanese wisteria twines clockwise.
Leaves are alternate, odd-pinnately compound, 4 to 16 inches (10-40 cm) long with 7 to 13 leaflets for Chinese wisteria and 13 to 19 leaflets for Japanese. Leaflets are oval to elliptic with tapering pointed tips 1.6 to 3 inches (4-8 cm) long and 1 to 1.4 inches (2.5-3.5 cm) wide. Young leaflets are quite hairy, but become mostly to completely smooth at maturity. Leaflet edges are smooth and wavy, and the petioles are very short.
Pinkish purple to blue-lavender pealike flowers hang in dense, pendulous clusters 6 to 12 inches (15-30 cm) long on the Chinese species, and all the flowers open at nearly the same time. Japanese wisteria inflorescence is 8 to 20 inches (20-50 cm) long, and the flowers open sequentially from the base to tip. Flowering usually occurs as the leaves are unfolding in April or May. Both species are fragrant, particularly Japanese wisteria.
Fruit is a flattened legume pod 2.5 to 6 inches (6-15 cm) long, tapering to the base, and constricted between the seeds. Pods are velvety hairy, greenish brown to golden and split open to release seeds. One to 8 flat round brown seeds 0.5 to 1 inches (1.2-2.5 cm) diameter ripen July to November.
Photo: J. Scott Peterson, USDA NRCS PLANTS Database, Bugwood.org
More images of Wisteria floribunda
Chinese and Japanese wisterias are popular ornamental plants, and each species has several named cultivated varieties. They are hardy and aggressive, capable of forming thickets so dense that little else grows. They constrict the stems of trees and kill them by girdling or over-topping. Wisteria belongs to the Fabaceae (Pea or Bean) family.
Wisteria is a perennial vine that may live for over 50 years. Vegetative reproduction is the primary means of expansion; numerous stolons develop new roots and shoots at short intervals. It will root at nodes when vines are covered with leaf litter. Wisteria can also produce abundant seeds if conditions are favorable, but flower buds produced in the fall are susceptible to winter kill. In riparian habitats, seeds may be dispersed downstream in water for great distances. Large seed size is a deterrent to animal dispersal.
Ideal habitat for wisteria is in full sun, but established vines will persist and reproduce in partial shade. Often they climb surrounding vegetation toward sunlight. Twining wisteria vines may reduce the vigor of competing vegetation by strangling the stems or shading the crown. Wisteria tolerates a variety of soil and moisture regimes wet to dry but prefers loamy, deep, and well-drained soil. Populations often spread from neglected gardens but are commonly found along forest edges, roadsides, ditches, and rights-of-way.
Origin and Distribution
Japanese wisteria was introduced from Japan around 1830 as an ornamental. It was popular in the southern U.S. as a decorative addition to porches, gazebos, walls, and gardens. Chinese wisteria is from China and was introduced in 1916. Wisteria is hardy enough to be found in New England, and a few areas farther north.
Other states where Chinese wisteria is invasive: HI, LA, LF, GA, SC, NC, VA, KY, IL, MD, NJ, PA, NY, MA.
Other states where Japanese wisteria is invasive: NJ, MD, VA, NC, SC.
Sources: Information on this plant page derived primarily from the Tennessee Management Manual and James H. Miller’s Nonnative Invasive Plants of Southern Forests, USDA Forest Service.
Cutting: Cut climbing or trailing vines as close to the root collar as possible. This technique is feasible on small populations, as a pretreatment on large impenetrable sites, in areas where a herbicide cannot be used, or if labor resources are not sufficient to adequately implement herbicidal control. This treatment will prevent seed production and strangulation of surrounding woody vegetation. Wisteria will resprout unless cut so frequently that its root stores are exhausted. Treatment should begin early in the growing season and be repeated at two-week intervals until autumn.
Grubbing: This method is appropriate for small initial populations or environmentally sensitive areas where herbicides cannot be used. Using a pulaski or similar digging tool, remove the entire plant, including all roots and runners. Juvenile plants can be hand pulled depending on soil conditions and root development. Any portions of the root system not removed may resprout. All plant parts, including mature fruit, should be bagged and disposed of in a trash dumpster to prevent reestablishment.
Cut Stump Treatment
Use this method in areas where vines are established within or around non-target plants or where vines have grown into the canopy. This treatment is effective as long as the ground is not frozen.
Glyphosate: Cut the stem 5 cm (2 in) above ground level. Immediately apply a 25% solution of glyphosate and water to the cross-section of the stem. This procedure may require a subsequent foliar application of glyphosate.
Triclopyr: Cut the stem 5 cm (2 in) above ground level. Immediately apply a 25% solution of triclopyr and water to the cross-section of the stem. A subsequent foliar application may be necessary to control new seedlings.
Foliar Spray Method
Use this method to control large populations. It may be necessary to precede foliar applications with stump treatments to reduce the risk of damaging non-target species.
Glyphosate: Apply a 2% concentration of glyphosate and water plus a 0.5% non-ionic surfactant to thoroughly wet all foliage. Do not apply so heavily that herbicide will drip off leaves. Glyphosate is a non-selective systemic herbicide that may kill non-target partially-sprayed plants. Ambient air temperature should be above 65°F.
Triclopyr: Apply a 2% concentration of triclopyr and water to thoroughly wet all foliage. Do not apply so heavily that herbicide will drip off leaves. A 0.5% concentration of a non-ionic surfactant is recommended in order to penetrate the leaf cuticle. Ambient air temperature should be above 65°F.