Wisteria. Wisteria is a genus of flowering plants in the legume family, Fabaceae, that includes ten species of woody climbing bines that are native to China, Korea, Japan, and the Eastern United States. Some species are popular ornamental plants. An aquatic flowering plant with the common name wisteria or water wisteria is in fact Hygrophila difformis, in the family Acanthaceae. The botanist Thomas Nuttall said he named the genus Wisteria in memory of Dr Caspar Wistar. Questioned about the spelling later, Nuttall said it was for euphony, but his biographer speculated that it may have something to do with Nuttall's friend Charles Jones Wister, Sr., of Grumblethorpe, the grandson of the merchant John Wister. Some Philadelphia sources state that the plant is named after Wister. As the spelling is apparently deliberate, there is no justification for changing the genus name under the International Code of Botanical Nomenclature. However, some spell the plant's common namewistaria. Genetic analysis shows Callerya, Afgekia and Wisteria to be each other's closest relatives and quite distinct from other members of the tribe Millettieae. Both have eight chromosomes. The following is a list of accepted Wisteria species: Wisteria brachybotrys-Silky wisteria. Wisteria brevidentata. Wisteria floribunda-Japanese wisteria. Wisteria frutescens-American wisteria. Wisteria macrostachya-Kentucky wisteria. Wisteria sinensis-Chinese wisteria. Wisteria venusta. Wisteria villosa. Wisterias climb by twining their stems around any available support. W. floribunda twines clockwise when viewed from above, while W. sinensis twines counterclockwise. This is an aid in identifying the two most common species of wisteria. They can climb as high as 20 m above the ground and spread out 10 m laterally. The world's largest known wisteria is in Sierra Madre, California, measuring more than 1 acre in size and weighing 250 tons. Planted in 1894, it is of the Chinese lavender variety. The leaves are alternate, 15 to 35 cm long, pinnate, with 9 to 19 leaflets. The flowers are produced in pendulous racemes 10 to 80 cm long, similar to those of the genus Laburnum, but are purple, violet, pink or white. There is no yellow on the leaves. Flowering is in spring in some Asian species, and in mid to late summer in the American species and W. japonica. The flowers of some species are fragrant, most notably W. sinensis. Wisteria species are used as food plants by the larvae of some Lepidoptera species including brown-tail. The seeds are produced in pods similar to those of Laburnum, and, like the seeds of that genus, are poisonous. All parts of the plant contain a saponin called wisterin, which is toxic if ingested, and may cause dizziness, confusion, speech problems, nausea, vomiting, stomach pains, diarrhea and collapse. There is debate over whether the concentration outside of the seeds is sufficient to cause poisoning. Wisteria seeds have caused poisoning in children and pets of many countries, producing mild to severe gastroenteritis and other effects. Wisteria, especially Wisteria sinensis, is very hardy and fast-growing. It can grow in fairly poor-quality soils, but prefers fertile, moist, well-drained soil. It thrives in full sun. It can be propagated via hardwood cutting, softwood cuttings, or seed. However, specimens grown from seed can take decades to bloom; for this reason, gardeners usually grow plants that have been started from rooted cuttings or grafted cultivars known to flower well.