My Wisteria is out of control and needs to be pruned. How do I prune it and when is the best time?
Wisteria can indeed grow out of control if not pruned on a regular basis. Two good prunings a year should keep the plant healthy and flowering happily. These are best done, once in mid-summer just after flowering and again in mid-September when vigorous growth has stopped.
For both of these prunings you should prune the entire plant back following the smaller branches back to where they join a larger branch. On the smaller branches, close to the joining, you will find nodes or buds. In mid summer, you want to cut the smaller branch leaving one or two of these nodes/buds as these will be where the plant will continue to grow. In the mid-September pruning you will leave four or five nodes/buds.
Overall, you need to keep in mind the shape of the plant, keep vigorous strong shoots and cut away branches that hang down. Dead, dangerous & diseased branches need to be removed as do overcrowded stems. When making your cuts, try and find a down facing bud/node and make your cut one half – one inch beside it, leaving the bud/node on the branch to form new growth.
Every third year, give the plant a more severe pruning as this will open up the plant, help keep it in the desired shape, allow light to penetrate the plant, encourage continuous flowering and take some weight off the support structure. Renewal pruning is usually done right after flowering and cutting back to within 7.5 centimetres of the main stem is advisable. Any suckers that grow from the root of the plant must also be taken off as many varieties of Wisteria are grafted onto rootstock and these suckers can crowd out the good plant. Also, remove any seed pods as you want the plant to put its energy into growth and flower production.
Wisterias bloom on the lower 30 centimetres of last years growth so by pruning back a couple of times a season, you can create a multi-branched stem with lots of flowers. Make sure to keep your cutting tools sharp and make clean cuts. Sterilizing tools when pruning will also cut down on disease spread in the garden.