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Wisteria is not a difficult plant to prune but its important its done correct or it can lead to wisterias not blooming as discussed in this guide. With this fast-growing climber, you do have to establish a pruning schedule and be sure to prune at the right times twice a year. Here’s how to do that and be rewarded with a wonderful display of blooms.
Though not technically a form of pruning, deadheading is the task of removing blooms from the plant when they fade. This encourages new blooms to come in the same growing season.
Do deadhead your wisteria flowers immediately after they fade. Do this by cutting off the bloom just above any new leaves or buds on the stem.
When to prune wisteria (and why)
You should prune wisteria twice a year. Prune the plant in the summer, ideally, between July and August. This allows the wood to ripen and to improve the likelihood of flower buds forming. Then prune again in the winter/early spring, in January or February. Pruning at this time encourages the development of short spurs that carry the flowers in the spring but also removes any access growth that would otherwise hide the flowers.
And always prune in dry weather.
In the first few years
The focus of your wisteria for the first couple of years should be to establish it on the trellis or other support structure. The point here is to make sure that it attaches itself to the wires of wooden slats firmly. Prune out the very low branches, train a few strong side shoots to climb and cut back the weaker side shoots. This will help form a good framework and don’t worry if you don’t get any flowers, it can take a couple of years until wisterias often start to flower.
Prune wisteria in the summer
Summer pruning is done to reduce the growth, allowing light and air to reach the new young foliage, this will also help encourage the growth that will produce the flowers.
Cut back the long, vigorous shoots to five or so buds from the base of this season’s growth. On older, mature plants, just cut back the side shoots to the framework of strong shoots. Remove any dead or diseased wood, down to where new green wood appears. This may be all the way to the base of the stem. Prune away any suckers at the base of the plant.
Prune wisteria in the winter
The aim here is to cut away any growth from the summer that’s too long or out of place and would otherwise hide the flowers in spring. This is a good time to work on reshaping your plant, either in its height or its width or just the general shape.
During the dormant season, tie in new growth to extend the main wisteria framework over the structure. Cut any remaining stems (the same ones you pruned in the summer) back to about 30cm from the ground and reduce all side shoots to about 5cm long. This ensures that the new flowers won’t be hidden by leaves.
Prune old wisteria plants
Sometimes older wisteria plants just wear themselves out. You need to hard prune these. Do this by cutting back the old branches to the central stem. Find new strong side branches to then tie in and start to create a new framework made from younger branches. Hard pruning stimulates growth in the wisteria but will also encourage lots of new growth. It’s also best not to feed wisteria after a hard pruning as it can encourage too much green foliage.