Plant Doctor Archive

Pruning wisteria

I'VE just moved into a garden with a wisteria, that is about five years old, growing over a pergola. How can I prune it so it flowers well and looks like the beauties I see in the open gardens during our rhododendron festival?

WISTERIAS flower best if their growth is restricted in some way. Left alone they can become quite rampant and may not put on a good display of flowers. For best flowering the ideal time to prune wisterias is during summer when you should prune back all new shoots to within three or four leaves from where they started. It's the buds at the base of these leaves that produce next spring's flowers.

You may have to prune several times over summer, usually starting around December, to keep long new growths trimmed back. The idea is to restrict growth, keep the plant under control and encourage flower bud initiation.

If your plant hasn't previously been summer pruned, then a winter prune could be useful now to help get it in a state that you can work with in summer. I suggest you prune back all long shoots that grew last summer, leaving about 10cm of growth at the base of each shoot. This may mean chopping out about half of all the growth there is. But don't be afraid - it will soon recover and you can then start a regular summer pruning schedule.

Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.