Wisteria is a woody climbing vine that develops new shoots each season, defying and overcoming obstacles to its inevitable progression in height. Even when installed in small gaps, wisteria thickens and can cause damage, particularly to building walls. For these reasons, it is imperative to control its fierce vegetative growth and, while we’re at it, to boost its flowering through various prunings depending on age, season and the gardener’s inspiration. 

When pruning wisteria, only keep the branches that are still in good condition at the end of winter. On these branches, only allow the first 3 or 4 buds to grow.  As for the new secondary branches, trim them down to a few inches and leave them only two remaining buds. Take this opportunity to shorten the main stems that appear too long, including those growing in spiral and those deemed unnecessary, before attaching them to a stake. This pruning technique stimulates the production of successive buds and provides up to 3 blooms per year.

Pruning according to the wisteria’s age 

During the first 2 to 3 years of its life, wisteria is pruned moderately, only to guide and secure it properly. It can thus be trained to produce 2 stems per head; each of which will flower in the 4th year. Thereafter, annual prunings will be severe to contain its vigorous growth and stimulate the renewal of secondary branches bearing flowers. After more than a decade, wisteria will need to undergo a rejuvenation pruning at its base. It is thus refreshed in order to bring down inflorescences that have been carried away in height because of the plant’s great age. After that procedure, the new shoots will be even stronger because they will benefit from the entire root system already in place.

Wisteria spring pruning 

This is done during March showers. The first thing to do is to cut the secondary branches entering their second year and that are still green. They are cut with shears and above the fifth leaf bud in order to save the plant’s sap in favour of the current year’s flower buds. To stimulate the plant’s ramifications, reduce, to a third of their length, all the stems not bearing flowers.

Pruning wisteria in summer 

After sufficiently developing from May to June, wisteria, with all its might, will tend to grow in places that should be preserved, such as downspouts, the roof base and telephone wires. It will then need to be thoroughly cut during the month of July, in order to prevent damage that could be caused by the plant through spreading, twisting or even due to its invasive growth covering all surrounding supporting structures. Secondary branches are also shortened, to about 8 inches. The main stem’s trellis training can also be strengthened. Let us also mention that Chinese wisteria can even be pruned in autumn to clear up its branches and facilitate the next winter’s pruning.

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Published in Flowering shrubs by Alexander on 04 Jul 2011