Wisteria is a genus of flowering plants in the legume family Fabaceae (order Fabales), comprising a small number of woody, twining vines native to East Asia — primarily China, Japan, Korea, and Vietnam — and to the eastern United States and southern Canada. The genus was established by the American botanist Thomas Nuttall in 1818, based on Wisteria frutescens, which he transferred from the genus Glycine.
The plants climb by twining their stems around available supports and can reach heights of 20 m (66 ft), spreading laterally up to 10 m (33 ft). The leaves are alternate, pinnate, 15–35 cm long with 9–19 leaflets. The most distinctive feature is the long, drooping raceme of fragrant flowers, which appear in shades of white, lilac, purple, and pink. Raceme length varies considerably by species: W. frutescens bears the shortest (5–7 cm), while W. floribunda produces the longest of any species (up to 90 cm, and over 120 cm in some cultivars). Flowering in Asian species occurs in spring as the leaves open; American species flower in mid to late summer.
Seeds are produced in pods resembling those of Laburnum. All parts of the plant contain a toxic saponin, wisterin, which can cause gastrointestinal illness and other symptoms if ingested. Wisteria also has nitrogen-fixing capability through Rhizobia bacteria in root nodules.
Among the most widely cultivated are W. sinensis (Chinese wisteria) and W. floribunda (Japanese wisteria), both introduced to North America in the early 19th century for horticultural use. Due to their vigour and tendency to escape cultivation, both are considered invasive species in parts of the United States, particularly the Southeast.
Etymology
The genus name Wisteria was coined by Thomas Nuttall in 1818 to honour the Philadelphia physician and anatomist Caspar Wistar (1761–1818), a colleague in Philadelphia where both men resided. The spelling differs from Wistar's surname; Nuttall attributed this to "euphony," though a connection to his friend Charles Jones Wister Sr. has also been speculated. An alternative spelling, wistaria, persists in some English usage.
Distribution
Wisteria species are native to East Asia (China, Japan, Korea, Vietnam), the eastern United States, southern Canada, and the region north of Iran. Asian species were introduced to western Europe — including England, France, and Germany — following their discovery, and Asian species have also naturalised in parts of North America where they were introduced for horticultural purposes.
Ecology
Wisteria foliage is used as larval food by certain Lepidoptera, including various moth species. All parts of the plant contain wisterin, a saponin toxic to humans and pets; the seeds are the most dangerous. The genus is capable of nitrogen fixation through symbiotic Rhizobia bacteria housed in root nodules, reducing its need for nitrogen-rich fertiliser in cultivation.
Cultivation
W. sinensis (Chinese wisteria) and W. floribunda (Japanese wisteria) are the most widely grown species, prized for abundant, colourful, and fragrant flowers. Both tolerate poor soils but perform best in fertile, moist, well-drained ground with full sun. Plants grown from seed can take decades to flower; grafted cultivars or rooted cuttings reach blooming age much sooner. Excess nitrogen fertiliser suppresses flowering; mature plants benefit from potassium and phosphate instead. Wisteria requires very sturdy support — mature specimens develop thick, heavy trunks capable of collapsing latticework or crushing thin posts. Pruning side shoots back to basal buds in early spring improves flower visibility; a compact, free-flowering form can be maintained by removing new tendrils three times during summer.
Taxonomy Notes
The genus Wisteria was established by Thomas Nuttall in 1818 based on W. frutescens, transferred from Glycine. Plants of the World Online (as of September 2023) accepts four living species. Several fossil species assigned to Wisteria have also been described, including W. fallax, W. kamtschatica, and W. shanwangensis. The genus belongs to the family Fabaceae, order Fabales. In several European languages (French glycines, German Glyzinie, Polish glicynia) the plants are still known under the older generic name Glycine.
