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Wisteria, or Wistaria, is a genus of about ten species of woody climbing vines native to eastern North America (United States) and east Asia (China, Korea, Japan). The vines climb by twining clockwise round the branches of trees, and can climb as high as 20-30 m above ground. The leaves are alternate, 15-35 cm long, pinnate, with 9-19 leaflets. The flowers are produced in pendulous racemes 10-80 cm long, similar to those of laburnum, but purple, blue, or white, not yellow. Flowering is in the spring (just before or as the leaves open) in some Asian species, and in mid to late summer in the American species and W. japonica. The flowers of some species are fragrant. The seeds are produced in pods similar to those of laburnum, and, like that genus, are poisonous.
The genus was named after Dr. Caspar Wistar (1761-1818), a professor of anatomy at the University of Pennsylvania.
Species
- Wisteria brachybotrys
- Wisteria floribunda - Japanese Wisteria
- Wisteria frutescens - American wisteria
- Wisteria japonica
- Wisteria macrostachya - Kentucky Wisteria
- Wisteria sinensis - Chinese Wisteria
- Wisteria venusta - Silky Wisteria
- Wisteria villosa
Cultivation
Wisteria can take decades to bloom when grown from seed; for that reason it is best to only grow plants that have been started from rooted or grafted cuttings of plants known to flower. Another reason for failure to bloom can be excessive fertilizer (particularly nitrogen). Wisteria has nitrogen fixing capability and thus mature plants should be given phosphate only.
Wisteria blooms on last year's growth, so cut back side shoots to 4 buds in early spring. In July, cut side shoots back to 12 inches. In the fall, cut side shoots back to six inches.