When & How to Prune Hydrangeas for Big, Beautiful Blooms! When to Prune: Bigleaf macrophylla prune after blooming late summer Panicle paniculata prune in late winter or early spring blooms on new wood Oakleaf quercifolia prune after flowering in summer blooms on old wood Smooth arborescens prune in late winter or early spring blooms on new wood How to Prune: 1. Remove dead or damaged stems 2. Thin older branches for airflow 3. Cut back healthy stems by for stronger growth Give each type the right trim, and theyll reward you with a burst of flowers!