The blizzard of white covering the Cherokee County landscape earlier in March came from the overabundance of the nefarious Bradford Pear trees. The white has now been replaced with a covering of purple Japanese/Chinese wisteria vines draping the trees and fences throughout the county.
Both the Bradford pear and Japanese/Chinese wisteria plant species are now considered invasive. Like the well-known kudzu vine, they seem to be destined to cover the county. Both the rootstock for the Bradford pear and the kudzu vine were introduced for economic reasons. The Chinese and its close cousin, the Japanese Wisteria were introduced as ornamental plants from China and Japan, the Chinese species in 1814, and the Japanese species in 1830. They are considered traditional southern porch vines.
Chinese Wisteria (Wisteria sinensis) and Japanese Wisteria (W. floribunda) produce long pinnately compound leaves and showy dangling clusters of purple to purplish-white spring flowers that appear before leaves. Chinese and Japanese wisterias are challenging to distinguish from one another due to possible hybridization. One interesting way to figure out which species you are looking at is how they twine around branches. Vines of Chinese Wisteria grow in a counter-clockwise direction (as do those of our native Wisteria). Japanese wisteria vines grow clockwise. Leaves are compound, about 1 foot long, with 7-13 leaflets on Chinese Wisteria and 13-19 on the Japanese variety. Leaves are alternate along the stem. Another way to distinguish between the species is their bark. Older bark of Chinese Wisteria is tight and dark gray with light dots (lenticels) compared to the white bark of Japanese Wisteria.
There are nine species of wisterias in North America and eastern Asia, including two native species. One of the two native species are the American Wisteria (W. frutescens), found from Virginia to Florida and Texas, and which is located in wet forests and edges. It sometimes forms large entanglements and flowers in June after leaves develop. The Kentucky wisteria (W. macrostachya) is native to Missouri, Tennessee, and Texas. Its purple raceme flowers of about 10 inches long appear in early June. The Kentucky wisteria is the latest blooming of all the wisterias.
The flowers of all the Wisterias are fragrant to various levels. I have noticed that bumblebees really like to visit it for the flower pollen, and you usually find an abundance of bumblebees visiting the flowers. Wisterias are legumes and produce long pea-like flowers in racemes and flattened pea-like legume seed pods from July to November. Chinese and Japanese wisterias are not fussy about soil. They can grow in poor soils, and in wet to dry sites.
The problem with Wisteria and its invasiveness is not with the native species but with Japanese and Chinese species. These deciduous high climbing, twining, or trailing woody vines can get out of control. Some vines can be up to 70 feet in length, and they form dense infestations where previously planted. Both colonize by vines twining and covering shrubs and trees and by runners that root at nodes when vines are covered by leaf litter. Once established in an area, wisterias may persist for a long time and eventually alter the environment that they inhabit.
Infestations of Wisteria can become are so dense that they strangle or shade out existing vegetation and displace native species. Heavy infestations can topple large canopy trees. The hard-woody vines twine tightly around host tree trunks and branches and cut through bark, causing death by girdling. On the ground, new vines germinating from seed or sprouting from rootstocks form dense thickets that smother and shade out native vegetation and impede natural plant community development. As girdled trees die, canopy gaps are created, which increases the amount of sunlight reaching the forest floor.
Because of its aggressive spread, the Georgia Exotic Pest Plant Council rates Chinese Wisteria as a Category 1 plant. A Category 1 plant is defined as an “exotic plant that is a serious problem in Georgia natural areas by extensively invading native plant communities and displacing native species.” Like the Bradford pear, my recommendation is not to plant Chinese or Japanese wisterias. There are other vine plant species that can provide the landscape effect that you might want to have from vines. These include the Coral vine, Swamp and Carolina Yellow Jessamine, Cross vine and trumpet vine.