Wisteria has been at the heart of garden art in Asia for centuries, and is also loved in Europe for its lush, abundant flowering and the vigour and duration of its foliage. It is also ideal for showy, high greening. The foliage growth is tremendous in early years, but will slow down after 10 - 20 years. Inadequate trellis planning or poor maintenance can cause considerable building damage, as wisteria is profoundly vigorous and strong. *This is a poisonous plant.
Wisteria sinensis // floribunda // frutescens
A location in full sun is best for wisteria; areas without direct sun (e.g. courtyards) or semi-shade are possible, but plants will produce fewer flowers. Distance between plants: 3 - 8 metres.
Wisteria is an extremely strong and vigorous twiner which can reach a height of 20 metres - a bit of a 'green octopus' - the young arms reaching a radius of more than 1 metre. It's light-fleeing shoots grow into crevices and nooks- sometimes with a cracking / blasting-effect on the structures they enter. Leaves are pinnate, usually light green, sometimes with an orange-brown halo. Foliage from May to November, rarely with yellow autumn colouring.
There are blue, white, and pink varieties in two main species: Wisteria sinensis (Chinese Wisteria) and Wisteria floribunda (Japanese Wisteria). There are several hybrids which are not easy to classify according to the direction of their twining, so an exact species identification of commercially available wisteria is sometimes not possible. W. sinensis flowers at the beginning of May, with a timid flowering at the end of the summer. W. floribunda flowers a little later. Another species, Wisteria frutescens (American Wisteria), develops flowers at an earlier age, but is vulnerable to frost. This mini-wisteria frutescens ("Long Purple" or "Amethyst Falls") is an alternative for warmer climates, is slower growing, matures earlier, is suitable for potting, and is less liekly to cause structural damage. With all purple wisteria: as the flowers start to open, they are delicious deep blue / violet / purple; fully open blooms fade to a greyish-blue. They often flower at the same time as lilacs. Has long, grey-green, hairy fruit-pods. Ungrafted plants often develop flowers only after several years, and tend to develop few(er) flowers.
*Summer and winter pruning should be carried out as shown in the photos. Regular pruning is absolutely essential to prevent damage to support systems.
Wisteria needs sturdy, preferably rod-like support systems, designed for the anticipated height and width of the plant. A simple linear system, rather than one that coves a large surface area; no wooden trellises. Wire ropes are suitable if the main trunk is trained strictly parallel to the wires, without twining, as illustrated in the photos. The short side branches are to be arranged so that any scratching of the wall is prevented should windy conditions make them move or twist the spindles. Lightning conductors, downpipes, and eave gutters, etc.. are not to be reached by the plant; all growth supports should have a distance of 2 metres from any such building elements and to the eave gutters-- to the sides as well as from the top. For suitable cable systems, see below. Use heavy or massive systems only; with potted plants or for wisteria frutescens, easy or medium systems will be adequate.