Each spring and fall when the subject of pruning hydrangeas comes up, eyes start spinning and minds start racing concerning the how, what, when and where of correct pruning of these popular flowering shrubs. Some of the different types of hydrangeas have similar fall pruning requirement, so I group them together to keep things simple.
The first group includes hydrangea macrophylla (the mopheads) and hydrangea serrata (the lacecap). Fall pruning here involves removing the spent blooms and any broken or obvious dead stems. The second group includes hydrangea paniculata (panicle cone shape flower) and hydrangea arborescens (white snowball flower). Fall and winter pruning of this group can, and should, be much more aggressive.
These hydrangeas should be cut back by one-third to one-half, and arborescens can actually be cut back to just a few inches above the ground. The third group includes hydrangea quercifolia (the oakleaf) and hydrangea anomala (the climbing). Minimal pruning here is best done in the spring.