Known for its luxuriant, drooping vines loaded with purple, pink, or white flowers that have a sweet fragrance, Wisteria can easily be the centerpiece of any garden if managed properly. There are two native American varieties but the Asian varieties, which originated in Japan, China and Korea, didn?t reach gardens in Europe and America until the 1830s, when intrepid plant explorers brought samples of the species from China and Japan home with them. Because transporting whole plants was impractical, these early explorers brought home seeds of the Wisteria vine instead.
What those early explorers cannot have imagined was that their prize specimens would take decades to bloom. Vines grown from seed are notoriously unpredictable, often waiting years or even decades to fully mature, so most gardeners prefer to plant cuttings from well-established, dependable plants.
Gardeners who find themselves with reluctant vines need not despair, however. Wisteria can be tricked into blooming early by engaging the plant?s defense mechanism. When the plant considers itself to be threatened, it will flower and produce seeds in an attempt to perpetuate itself before its death. By purposely damaging the root system, gardeners can trick a plant into engaging in this survival strategy. Placing the vine under such severe stress won?t kill it, but it is also not ideal, as it involves destroying part of the plant?s ability to take in nutrients.
Given how reluctant Wisteria can sometimes be, it is surprising that its also considered something of a pest in certain areas. Its vines can have a tendency to take over and choke out native species when they're well-established, as they have done in parts of the American Southeast.
Vines do best in full sun, and prefer fertile, moist, well-drained soil. However, they can grow even in poor soil by utilizing nitrogen fixation, just as their cousins in the legume family do. A kind of bacteria, called rhizobia, attaches to the plant?s root system. Once there, the bacteria happily converts atmospheric nitrogen into a form that the plant can use for its nutritional needs. As a by-product of this mutually beneficial relationship, Wisteria vines actually enrich the soil in which they grow.
Wisteria is among the class of plants known for twining and climbing as they grow. Some plants will follow the sun, and twine in a clockwise direction. Wisteria is able to twine in either direction, both clockwise and counter-clockwise. It is best to let the vines train and twine around something very sturdy. The plant will send out tender, flexible shoots at first, which will later become quite hardened and woody, pulling things like drainpipes away from the sides of buildings if not corrected in time.
The vines should be allowed to grow into their desired shape first before attempting to prune it. Once it has spread over an area, the tender new shoots of the plant may be trimmed back in late June or early July to keep the vines blooming and looking tidy. The ends of the main framework of vines may also be cut, in order for the plant to maintain its overall shape. During the winter months, the side- shoots may be shortened to just three or four inches in length. This can be quite a difficult process for a very large vine, but it will keep the plant flowering and compact.
When purchasing vines, it is best to know the parent from which the plant was cut or grafted. For example, if the identification tag merely states ?Wisteria floribunda,? you know which species you are buying, but not if that particular cutting is one that is likely to bloom in your lifetime. If, however, the species name is followed by a name like ?Texas Purple,? you can be assured that the plant is from a specific, dependably-flowering parent plant. Cuttings and grafts of vines can be found in most garden centers or nurseries. There are also mail order catalogs which can be a good resource, as long as you always check the plant?s parentage. It is generally best to buy a grafted plant, which should bloom within three years.
Some species of Wisteria flowers have been used to make wine, and can be added to tossed salads for an exotic touch. However, only experienced taxonomists and plant specialists know the difference between the toxic and edible varieties, so it is best to always err on the side of caution. Wisteria is grown for its spectacular ornamental beauty, rather than for any use it might have in the kitchen. The largest vine ever recorded grows in California. At more than an acre wide, it weighs 250 tons.