Pruning old wisteria

(Question)

Our old and healthy wisteria needed to be cut back for repairs on the deck and pergola. I cut it back be about half, keeping only the four main branches to a length of about 14 feet. The wisteria was cut back two weeks ago on April 9 (bad timing I know!). I have not yet seen any sign of new growth and am worried I have damaged the plant. How long should I expect to wait before I see some sign of life?

(Answer)

Thank you for contacting the Toronto Master Gardeners with your inquiry concerning your Wisteria.

I would not quite give up on your wisteria just yet. A plant not leafing out is most likely due to weather conditions. We recently had a cold snap just after having a week of beautiful warm weather. Check the flexibility of a stem. If it bends easily, it’s probably alright. If it is dead, the stem will snap and break off. Or, scrap a little of the outer bark away with your fingernail: if you see green wood this means that the plant is still alive and it is just taking its time for the leaf buds to expand.

I also have a wisteria growing on a trellis and within the last few days the flowering buds have started to open up. However the leaf buds are still tightly closed.

According to the Royal Horticultural Society article Wisteria Pruning: “hard pruning maybe required where maintenance needs to be carried out on the structure supporting the plant. Drastically shortening back long branches, removing sections of older stems to just above a strong young branch or growth shoot lower down, or cutting completely back to a main branch, or even to ground level may be necessary.”

Hard pruning will stimulate new growth and as a result it is recommended that you do not fertilize your vine during the first spring after hard pruning.