How to Prune a Wisteria Vine
Wisteria is a special case, where shortening the sideshoots promotes the formation of flower buds.
Step 1: Pruning Sideshoots
In summer, after flowering, prune back the sideshoots to within five to seven leaves from the main stem, and tie in new growth.
Step 2: Shorten New Stems
In winter, shorten the new stems that have formed after you pruned in summer. Take these back to leave two buds. The short sideshoots that are left will produce lots of spring blooms.