Wisteria

Wisteria sinensis // floribunda // frutescens

The Wisterias are popular for their abundance of flowers and vigorous growth habit. Wisteria has been known for centuries in the Asian art of gardens. There are several hybrid forms which cannot be identified according to the direction of their twining  etc, hence an exact species identification based on eg the twining (right or left) of available Wisterias is almost impossible. A poisonous plant. Inadequate espalier planning and maintenance can cause considerable building damages.

Requirements

Position in full sun is best, areas with no direct sun but a high light density (eg courtyards) or semi-shade are possible, but plants will produce less flowers.

Growth and Leaves

An extremely strong and vigorous twiner, which can reach 20m height, a “Green Octopus” - the young strangling arms reaching an action radius of more than 1m.  Light-shunning growth, into nooks and crannies etc, with blast-effect. Feathery leaves, mostly light green, sometimes with an orange-brown tinge. Foliage from May to November, rarely with yellow autumn colouring.

Two ancient Wisterias
Second blossoming of Wisteria in midsummer
Stainless steel growth support with generous distance from wall.

Flower and Fruit

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. Fruit are long hairy pods. Non-grafted specimens often develop flowers after many years only, and in some cases bear but a few flowers.

Downpipe damaged by Wisteria, after unwinding the strangling stem to the left
Stems are slightly bent and guided around wall brackets in an arching form, to prevent the plant from growing into the brackets in the future. Continue below.
The healthy foliage lasts well into autumn
Rope system, heavy duty assembly kit. Already in the first year, the twining shoots of solitary plants reach 4-6m height, and should then be reduced to one stem per wire rope and unwound from the rope (see below).
A year later, after leaf fall the entangled shoots need to be disentangled again and pruned. The fastenings on the future main stem are replaced. Continue below.

Growth Support Systems

Sturdy, preferably rod-like support systems, designed for anticipaded height and width of plant. A simple linear system rather than covering large areas, no timber trellises. Wire ropes are suitable if the main stem is guided strongly 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 render is prevented should windy conditions make the newel and hence the plant turn around. 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 Duty Systems, in case of pot plants Light or Medium systems will be adequate.

Pruning

Summer and winter pruning as illustrated in photos. Regular pruning is absolutely essential to prevent damage to support systems.

Unwound Wisteria shoot guided parallel to the wire rope, in winter. This shoot is now trained as a main stem with short side shoots; the fastenings have to be checked regularly in the following years, and if required, replaced. Continue below.
Wisteria kept in shape by summer pruning
Strongly structured and pruned Wisteria on a house wall in winter, guided along wire rope. Such a spartan stem support is necessary to prevent building damage.
The same Wisteria in the following midsummer, illustrating an exemplary summer cut.
Wisteria on wire rope. Two single stems develop such lush foliage anew every summer!
By guiding the stem parallel to the wire rope as described on the left, such deformations can be prevented (overstretched rope and bent wall bracket).
Ingrown balustrade rod. In contrast to wire ropes, rods cause less building damage than ropes, nevertheless permanent twining is to be avoided.
Pruning: Already in summer, the (side) shoots are trimmed back regularly to approx. 30-40cm, to encourage flower producing woody stems. In winter (refer photo above), they are trimmed again down to about 3 buds. From these burgeons the flower buds will grow in the following spring. (Photo below).
These two Wisterias are kept in shape with rigorous pruning.
Magnificent flower abundance of a Wisteria
Already after 10-15 years such trunks can be expected in Wisterias
Ancient Wisteria on a pergola in the Sankeien Garden in Yokohama / Japan. Photo: Regine Hartkopf
After completed maintenance: here the fastening was done with flexible and adjustable vulcanised india-rubber bandages. Some emerging flower buds can be seen on the side shoots.
As an alternative to expensive growth support systems, pre-trained solitary specimens can be planted and trained onto columns or similar, and fastened with flexible velcro tape or elastic bands.
Overstretched and ingrown wire rope
Rope wire "for breakfast:" this Wisteria is still 'chewing away' on its ripped out support system...

Suitable growth support systems for Wisteria

Please click on the graphic illustrations !

 = suitable               = moderately suitable               = unsuitable