For pruning caney shrubs (forsythia, spirea, nandina, mahonia….) the principle is simple. Prune from the base of the shrub. Remove about one-third of the oldest canes and any weak or crossing canes, taking them all the way to the ground. For flowering shrubs, this should be done just after flowering to prevent removal of next season’s flower buds. This method assures flowering is maximized (since all canes are young and vigorous) while the form of the shrub is maintained.