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Wisteria has two types of wood: the main, thick, eventually woody vines, which are the support structure, and much thinner side shoots (laterals) coming off it, which carry all the flowers.
The main purpose of yearly pruning is to maximise the flowering at the base of the side shoots, by removing the excess, whippy, leafy growth at the end of those side shoots, which won’t flower.
When to Prune Wisteria?
The Essential Winter Prune
Wisteria should always be pruned in winter to early spring (January to February is good, but anytime when the leaves are off is fine too), when there are no frosts forecast for at least 48 hours.
The side shoots (which carry the flowers) must be cut back to 2-3 buds from the main, woody stem.
If you are wondering “why hasn’t my Wisteria flowered?”, the most common reason is that it wasn’t pruned around this time!
If you do not prune Wisteria around this time, it will wake up in Spring and quickly produce a lot of leaves at the expense of the flowers, which will be partially hidden by that lush foliage.
The Recommended Summer Prune / Tidy Up
During summer, when the flowers have finished, trimming those flower-bearing side shoots down to 5-6 buds from the main stem.
If you miss this trim one year, it’s fine, the winter pruning is adequate, but it is highly recommended for best performance (and for controlling this vigorous vine in a cosy garden!).
Summer is also the time to extend any main stems by leaving well-placed shoot/s untrimmed, and tying them into the support framework.
Cutting back your Wisteria in winter is all about directing the resources of the awakening plant exclusively to the bases of the lateral shoots, which is where all the flower buds are.
Pruned correctly, Wisteria should look and feel like this:
How to Prune Wisteria?
This beautifully short video by the RHS shows you how to carry out both summer and winter pruning.
You will need some garden secateurs (known as snips round here), and if cutting out large main stems, a set of bypass loppers is usually sufficient – very old wood will need a pruning saw.
One of the best all-round Wisteria mini-documentaries online is this one by garden & landscape designer Ian Cooke.
He speaks so clearly that you can set the playback speed to 1.5x and hear him perfectly well.
And this is a great video specifically for tackling a mid-sized Wisteria that’s well established on the side of a house, but still needs training to fill the desired space.
It reminds you to watch out for drainpipes & gutters, which Wisteria will destroy if you let it!
So be sure to tidy up your Wisteria before February is out, or else you may get a visit from the Wisteria inspector, who could revoke your Wistering licence, and no one wants that.
Beware the Wisteria Inspector