Wisteria needs pruning twice a year to keep it floriferous and to prevent it from growing out of its allotted space.
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.
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 leaves.
Summer pruning: about two months after flowering, tie in the new, long shoots on to trellis or stout wires.
Summer pruning: New shoots that are not needed or have grown in already crowded areas should be pruned. Cut them back to five or six leaves from the main branch, making the cut just above that leaf.
Winter pruning: Long, whippy shoots that grew after the summer pruning should also be pruned. Cut these back to five or six buds from the main branch, making the cut just above a bud.
Winter pruning: In January or February shorten summer-pruned shoots further. Cut them back to within 2.5–5cm (1–2in) of older wood, or 2 to 3 buds.