Hauntingly fragrant spring or summer blooms cascade from wisteria (Wisteria spp.) vines as gracefully as Spanish moss trails from the limbs of ancient Southern oaks. The U.S. Department of Agriculture reports four varieties of wisteria growing wild across the eastern United States. They include one native and two introduced varieties. The fourth resulted from natural hybridisation of the introduced species.
Chinese (Wisteria sinensis) and Japan (Wisteria floribunda) didn't find widespread use outside their native habitats until well after British botanist Mark Catesby shipped native American wisteria (Wisteria frutescens; Wisteria macrostachya) plants to his London acquaintances in 1724. The American vines enjoyed exceptional popularity as garden ornamentals in England and Europe for nearly a century. Chinese wisteria (Wisteria sinensis) arrived in England, courtesy of the East India Company's Captain Robert Welby, in 1816. By 1830, Chinese and Japanese wisterias had replaced most American wisterias in Europe and were growing on arbors, trellises and porch columns across the Southeastern United States.
Twining Direction Differences
One physical difference between American and Chinese wisterias and their Japanese counterparts is twining direction. Northern Hemisphere plants, American and Chinese wisteria, wind in a counter-clockwise, left-to-right direction. Gravity affects Northern Hemisphere sinks and bathtubs in a similar fashion; draining water always circles from left to right. Although Japan also lies in the Northern Hemisphere, it arrived there after floating north a few centimetres each year over millions of years. Japanese wisteria, however, never lost its Southern Hemisphere, clockwise-twining habit.
Wisteria x Formosa
Wisteria x Formosa is a naturally occurring, hybrid offspring of Chinese and Japanese wisterias. The USDA Natural Resources Conservation Service reported populations of the hybrid in two Florida and three Louisiana counties, as of 2011.
Native American Wisterias
American wisteria (W. frutescens) and Kentucky wisteria (W. macrostachy) tolerate winter temperatures to U.S. Department of Agriculture plant hardiness zones 4 and 5 respectively. American wisteria's lilac-hued, early-to-midspring flower clusters open in 6-inch clusters as its deep-green, feathery compound leaves unfurl. The 15- to 30-foot vine occasionally produces lighter flushes of summer flowers. Kentucky wisteria's yellow-tinged, purple blooms cascade up to 1 foot from leafless spring branches. The Blue Moon cultivar, cold-hardy to zone 3, has simultaneously opening blue early-summer flowers on 15- to 25-foot branches.
Japanese wisteria typically climbs to 35 feet, with 10- to 15-inch, bright-green compound leaves. Its fragrant, midspring blooms, ranging from red- to blue-violet, measure up to 20 inches long. The vine's grey-barked trunk develops a sculpted appearance with age. Cultivars of the zone 5-hardy vine include white-flowering Ivory Towers and Snow Showers, with rich fragrance and up-to-2-foot flower clusters.
Its counter-clockwise twining habit is one of the few characteristics distinguishing Chinese from Japanese wisteria. Also hardy to zone 5, Chinese wisteria produces 10- to 25-foot stems of faintly scented, blue-purple spring blooms simultaneously with its unfolding foliage. Its trunks also twist with age. The Prolific cultivar features 6-inch to 1-foot, lavender-blue blossoms. The flowers open earlier and continue blooming longer than those of the species vines.