With the continuing popularity of the many types of hydrangeas available to gardeners, there remains quite a bit of confusion as to how to properly prune these shrubs. The problem is that there are four very different types of shrub hydrangeas, each with multiple cultivars, and each type requires a different pruning procedure.
The most intimidating to prune are the extremely popular mophead or bigleaf hydrangeas, Hydrangea macrophylla, which include all of the ‘Endless Summer’ cultivars, sold in distinctive blue pots. These have been revolutionary for area gardeners since the older, less-hardy cultivars bloom only on year-old stems, and in our climate zone they often died to the ground, with the resultant loss of old stems and flower buds. The new growth develops into lots of foliage, but no flowers. The ‘Endless Summer’ series are “remontant”, which means they bloom on both year-old and new (current year) stems. It is important to just lightly prune the stems back to any swelling buds in the spring. These buds will provide flowers in early summer. Never cut stems to the ground unless a severe winter has killed the plant back to the roots. If the latter has unfortunately happened, the new stems that come from the roots will bloom in late summer into the fall. Regardless, to have a healthy mophead hydrangea, be sure to provide it with soil enriched with lots of compost, and water regularly.
The second group of hydrangeas is Hydrangea arborescens, the most famous of which is the undemanding and extremely reliable ‘Annabelle’, around for over 100 years. In recent years, new cultivars have been introduced, including ‘Incrediball’ and ‘Invincibelle’. This is the most easy and foolproof group of hydrangeas to prune. Simply cut the whole plant to the ground in late fall or early spring. Robust new growth will erupt with warm weather and a bountiful display of blooms is assured.
The third group is Hydrangea paniculata, or Panicle Hydrangea, an increasingly popular group of spectacular blooming plants that include ‘Pinky Winky’, ‘Bobo’, ‘Little Quick Fire’, ‘Firelight’, and ‘Strawberry Sundae’. There is a cultivar for every garden, big or small, as they mature in size from 3’ to over 9’. All varieties bloom on new wood, so pruning involves just cutting back the old, faded flowers and long stems to get a rounded form (not to the ground as with the last group), ready to sprout in late spring, flowering in summer.
The last group is Hydrangea quercifolia, the Oakleaf Hydrangea. Cultivars range from the dwarf ‘Ruby Slippers’ to the huge ‘Snow Queen’, and its worth seeking out named cultivars which have better bloom performance compared to the species. Oakleaf hydrangeas bloom on old wood, which means they should be pruned only to shape as needed. If the proper cultivar is used, even pruning to maintain size will not be required.
There is a hydrangea for every landscape. They are undemanding and long-lived. Enjoy them without worrying about how to prune them.