Wisterias can be left to ramble unchecked where space allows but will usually flower more freely and regularly if pruned twice a year. The removal of growth in summer allows better air circulation and more sunlight to reach the base of the young growths, encouraging better ripening of the wood and improving the chances of flower bud formation. Restricting the amount of vegetative growth and encouraging short, flowering spurs will result in more flowers.
HOW TO PRUNE WisteriA
Wisteria is pruned twice a year, in July or August, then again in January or February.
July or August
Cut back the whippy green shoots of the current year’s growth to five or six leaves after flowering in July or August. This controls the size of the wisteria, preventing it getting into guttering and windows, and encourages it to form flower buds rather than green growth.
January or February
Then, cut back the same growths to two or three buds in January or February (when the plant is dormant and leafless) to tidy it up before the growing season starts and ensure the flowers will not be obscured by leave.
With older plants severe pruning may be needed to remove old, worn-out growths, or branches growing over windows or protruding outwards from the face of the building. Likewise, 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. The end result should be a skeleton frame work of reasonably well-spaced branches.