Scientific Names: Wisteria floribunda, Japanese wisteria
Wisteria sinensis Chinese wisteria
Common name: Wisteria (referring to both species throughout this fact sheet)
Family: Fabaceae
History & Introduction
Japanese and Chinese wisteria are native to Japan and China, respectively. Both species were brought to the US in the early 1800s for use as a horticultural plant. As a vining plant with attractive purple flowers, it was, and still is today, used to decorate porches, gazebos, walls of homes and buildings, gardens and parks.
Today, wisteria is a wide-spread invasive species in the United States, with a range as far west as Texas, and as far north as Maine. Within LIISMA it is ranked as a Tier 4 invasive species.
Due to their similarity, as well as ability to hybridize, identifications of wisteria species may often be inaccurate. Functionally, both Chinese and Japanese wisteria are detrimental to our ecosystem.
Identification
Habit: Herbaceous perennial that can be seen vining, climbing or growing horizontally on the ground. Each species can grow up to 65 ft in a tree canopy. ID Tip: Chinese wisteria vines twine clockwise, while Japanese wisteria vines twine counter-clockwise
Leaves: Compound, ~1 foot (0.3 m) long, alternating along the stem. Japanese wisteria leaves have 13 to 19 leaflets, while Chinese wisteria leaves have 7 to 13 leaflets
Stems: Older wisteria plants may grow to 15 inches (38 cm) in diameter, with infrequent, alternate branches.
Flowers: Wisteria flowers are dangling and showy, blue-violet, and are borne on racemes. Racemes are 4 to 20 inches (10-50 cm) long and 3 to 4 inches (7-10 cm) wide. All Chinese wisteria flowers bloom at the same time, while Japanese wisteria flowers bloom in sequence, starting at the base.
Fruit: Wisteria fruits are velvety brown legumes, 4 to 6 inches (10-15 cm) long, narrowed toward the base, with constrictions in the pods that separate the seeds. Each pod contains 1 to 8 flat, round, brown seeds, each 0.5 to 1 inch (1.2-2.5 cm) in diameter.
Roots: Deeply rooted, with nitrogen fixing nodules.
Phenology: Flowers in spring (April-May); Fruits present July to November.
Native Lookalikes:
Native American wisteria (Wisteria frutescens), while uncommon, also occurs in the north eastern U.S. You can differentiate it from Japanese and Chinese wisteria as American wisteria produces purplish to white flowers later in the year (June – August) and has smaller (5-10 cm), non-hairy seedpods
Habitat
Wisteria can tolerate a wide range of habitats, from mesic soils to more well drained soils, even sandy beaches. As a legume, it can exploit very nutrient poor soils and those that are heavily eroded through the use of its nitrogen fixing root nodules. Can be found in disturbed trail edges, right of ways, roadsides, and riparian zones. It prefers full sun, but can still thrive in shady areas.
Damage
Vines can strangle and girdle trees, which can weaken or kill trees outright. As the woody stems of wisteria wind around tree trunks and branches, their stems and leaves can increase moisture on the tree, which can increase the tree’s susceptibility to pests and disease. The increased weight on stressed trees can make them more hazardous, and in a strong storm could cause them to fall over. When tree canopies collapse due to wisteria vine damage, increased light can allow for greater wisteria growth.
Wisteria vines are extremely long lived, with some reports saying some individuals could live up to 100 years.
Dispersal
Spread of wisteria is mainly through vegatative rhizomes and stolons which root at each node. Fragments of this plant can grow into new plant parts. As well, stems can resprout after cutting. Wisteria seeds are relatively large and heavy, and may be transported by animals or accidentally by humans.
Prevention
Do not plant wisteria. Treat wisteria on your property when it is young to prevent further growth and seed formation. Wherever you see wisteria growing in natural areas, please document it in iMapInvasives or iNaturalist. Remember to clean your gear before and after you leave a site to prevent the spread of invasive species like wisteria. After cutting/mowing wisteria, or on sites with wisteria, remember to clean your equipment to ensure no wisteria plant fragments or seeds will be transported.
Control
Chemical control:
The pesticide application rates and usage herein are recommendations based on research and interviews with land managers conducted in the Lower Hudson Prism. When considering the use of pesticides, it is your responsibility to fully understand the laws, regulations and best practices required to apply pesticides in a responsible manner. At times, the pest you seek to treat may not be on a pesticide label, requiring a 2ee exemption from NYSDEC. Always thoroughly read the label of any pesticide and consult the NYSDEC or a licensed pesticide applicator with questions.
- Foliar Spray: High rates and repeat applications of foliar spray are necessary to come close to eradication of Chinese wisteria populations. Application is most effective in warmer temperatures and should be performed from June-September. A follow up application is advisable 3-6 weeks after initial treatment. This method of management should be performed only in areas where the much more effective cut-stump methods would be impractical. Always read and follow all instructions on the herbicide label.
- Cut Stump: Cut stump herbicide application is an effective way of managing Chinese wisteria, however, high rates of chemical application must be employed (25% solution of glyphosate or triclopyr in water). Furthermore, this method can only efficiently be used on larger vines with a greater surface area. Treatment should be performed during the latter half of the growing season and repeat treatment may be necessary to kill root sprouts.
- Basal Bark: Treat with a 15-30% solution of triclopyr in oil.
Manual control: Pulling/digging up. Pulling as a control method is possible only if plants are very young. Once wisteria becomes woody it is very difficult to remove by physical means. Any root fragments left in soil have the potential to re-sprout.
Horticultural Alternatives
American wisteria (Wisteria frutescens)
Trumpet creeper (Campsis radicans)
Trumpet honeysuckle (Lonicera sempervirens)
Dutchman’s pipe/pipevine (Aristolochia macrophylla)
Sources
https://www.fs.fed.us/database/feis/plants/vine/wisspp/all.html
https://www.lhprism.org/species/wisteria-sinensis
https://wiki.bugwood.org/Wisteria#Similar_Native_Species
