Hydrangeas are popular additions to the home landscape. These woody shrubs provide lush foliage and long-lasting blooms in every garden. Knowing when or if they should be pruned is a homeowner’s dilemma. The answer begins with knowing which species of hydrangea you have in your garden. The flowering pattern – does it bloom on new wood, old wood, or new and old wood? – is one tool to help identify the species. Another clue is the leaves – are they smooth, serrated, or do they resemble oak leaves?
Smooth and panicle hydrangea bloom on new wood. In late winter or early spring, before new growth emerges, prune these shrubs (as well as others that bloom on new wood) using either the renewal or rejuvenation pruning method.
The most commonly grown cultivar ‘Annabelle’ was first discovered in southern Illinois. A clump-forming shrub with heart-shaped leaves and huge flower heads, ‘Annabelle’ hydrangeas bloom in June and again in August and respond best to rejuvenation pruning.
Panicle hydrangeas are deciduous shrubs often native to Asia, with large cone-shaped flower panicles. These hydrangeas benefit from renewal pruning annually and a rejuvenation pruning every few years.
Four species of hydrangea that flower on old wood and should not be pruned in late winter or early spring are: Bigleaf hydrangeas (H. macrophylla), Oakleaf hydrangeas (H. quercifolia), Mountain hydrangeas (H. serrata), and Climbing hydrangea (H. anomala subsp. petiolaris). For more details on Hydrangeas check out the Ohioline Fact Sheet “Selecting Hydrangeas for the Home Landscape” at https://ohioline.osu.edu/factsheet/hyg-1263