Chinese wisteria

Appearance

It can grow 20–30 m long over supporting trees by counterclockwise-twining stems. The leaves are shiny, green, pinnately compound, 10–30 cm in length, with 9-13 oblong leaflets that are each 2–6 cm long. The flowers are white, violet, or blue, produced on 15–20 cm racemes in spring, usually reaching their peak in mid-May. The flowers on each raceme open simultaneously before the foliage has expanded, and have a distinctive fragrance similar to that of grapes. Though it has shorter racemes than "Wisteria floribunda", it often has a higher quantity of racemes. The fruit is a flattened, brown, velvety, bean-like pod 5–10 cm long with thick disk-like seeds around 1 cm in diameter spaced evenly inside; they mature in summer and crack and twist open to release the seeds; the empty pods often persist until winter. However seed production is often low, and most regenerative growth occurs through layering and suckering.

Distribution

It was introduced from China to Europe and North America in 1816 and has secured a place as one of the most popular flowering vines for home gardens due to its flowering habit. It has however become an invasive species in some areas of the eastern United States where the climate closely matches that of China.

Habitat

It is hardy in USDA plant hardiness zones 5-9, and prefers moist soils. It is considered shade tolerant, but will flower only when exposed to partial or full sun. It will also flower only after passing from juvenile to adult stage, a transition that may take up to 20 years. It can live for over a hundred years.

Defense

All parts of the plant contain a glycoside called wisterin which is toxic if ingested and may cause nausea, vomiting, stomach pains, and diarrhea. Wisterias have caused poisoning in children of many countries, producing mild to severe gastroenteritis.