At least four different species of vines in the pea family (Fabaceae) produce purplish flower in clusters that resemble grapes. While all commonly have names called "wisteria," they include both the botanical genus of Wisteria and Millettia. Fertile, moist, well-drained soils in sunny locations help these vines produce an abundant display of flowers. Depending on species, the blooms occur in spring, summer or earliest fall.
Blooming in late spring, the Chinese wisteria vine (Wisteria sinensis) grows vigorously with woody stems 30 feet or longer. Looking at an individual flower in the grapelike pendant cluster reveals a pea-shaped blossom that is evenly coloured lavender/lilac blue. The flowers open about the same time as the feather-like leaves unfurl. After blooming, beanlike velvety green seed pods develop, about six inches long. The University of Florida lists Chinese wisteria as an invasive/noxious weed that plagues many landscapes across the United States. It survives in U.S. Department of Agriculture Hardiness Zones 5 through 8.
Native to the American Southeast, American wisteria (Wisteria frutescens) grows less rampantly and isn't a problematic, spreading weed like the Chinese wisteria. American wisteria grows 15 to 25 feet tall and its violet purple flowers appear in early summer and sporadically up until early fall. According to the Learn2Grow website, a common garden variety seen in the United States is called Amethyst Falls. Grow this wisteria species in USDA Zones 6 through 10.
Typically encountered only in warm winter regions, the evergreen wisteria (Millettia reticulata) becomes deciduous if the mild winter gets a bit too chilly. Native to the subtropical parts of southern China, evergreen wisteria matures with heavy, thick vining branches up to 22 feet tall. Anytime in the warmth from spring to fall, pointy clusters of wine-purple to violet flowers appear. Each blossom bears a tiny yellow throat inside the lower petal called a keel. The fragrance smells like camphor, not sweet like those of true Wisteria species. Evergreen wisteria vine grows in USDA Zones 7 through 10.
From Japan, the Japanese wisteria (Wisteria floribunda) escaped cultivation in the United States and grows as a pesky naturalised weed much like Chinese wisteria. In mid spring this woody vine displays its blue-violet flower clusters as the leaves emerge. The upright petals, called standards, reveal yellow or white spots. Growing up to 28 feet tall, the University of Connecticut mentions Japanese wisteria's twining stems spiral around something in a clockwise fashion when viewed looking down on the stem. This helps identify it from the counter-clockwise stem spiralling seen on the Chinese wisteria. Japanese wisteria is hardy in USDA Zones 5 through 9a.