Wisteria has been at the heart of garden art in Asia for centuries, and is also popular here for its abundance of flowers, and the vigour and duration of its foliage; it is also ideal for high greening. There are several hybrid forms which cannot be identified according to the direction of their twining etc., so an exact species identification based on the twining (right or left) of available wisterias is almost impossible. The foliar development of wisteria is spectacular when young, but slows down after 10 - 20 years. Inadequate espalier planning or poor maintenance can cause considerable building damage. This is a poisonous plant.
Wisteria sinensis // floribunda // frutescens
A location in full sun is best; areas with no direct sun but a high light density (e.g. courtyards) or semi-shade are possible, but plants will produce fewer flowers. Distance from plant to plant: 3 - 8 metres.
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 or blasting-effect to the structures it enters. Feathery leaves, mostly light green, sometimes with an orange-brown tinge. Foliage from May to November, rarely with yellow autumn colouring.
There are blue, white, and pink varieties in two main groups: Wisteria sinensis (Chinese Wisteria) and Wisteria floribunda (Japanese Wisteria). W. sinensis flowers at the beginning of May, mostly before the shoots appear, followed in midsummer by some sparse flowers. W. floribunda flowers a little later. Another species, Wisteria frutescens (American Wisteria), develops flowers at an earlier age, but is frost tender. Opening flower buds deep blue and deep purple, fully open flowers soon fading to a grey-blue. Flowers often simultaneously with lilac. Has grey-green long, hairy fruit-pods. Non-grafted specimens often develop flowers after many years only, and in some cases, bear but a few flowers.
Summer and winter pruning as illustrated in 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 covering large areas; no wooden trellises. Wire ropes are suitable if the main trunk is guided 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 rope systems, see below. Use heavy or massive systems; in the case of potted plants or for wisteria frutescens-- easy or medium systems will be adequate.