Chinese wisteria (Wisteria sinensis) is aggressive, but you can trim it aggressively without hurting it. Prune it after flowering and again once or twice during the summer, when you should trim back fresh long shoots to the principal stems. If necessary, prune the overall form in winter, retaining a main trunk and dense branching structure. Avoid removing the spur shoots (compact, woody stems with short internodes). These spurs, which come out of the major stems, are where most blooms appear.