A: I’m glad you asked this because this is National Hydrangea Week. There are several types of hydrangeas, and it makes a difference when to prune them. Woody plants have old and new wood. New wood is the season’s new growth. The branch will have leaves on it. If a plant loses its leaves over the winter, in the spring all those leafless branches are old wood.
Bigleaf hydrangea (Hydrangea Macrophylla), climbing hydrangea (H. anomala petiolaris), and oak-leaf hydrangea (H. quercifolia) flower in early summer on old wood. They set next year’s flower buds on existing wood shortly after flowering, so pruning is best done immediately after flowering. If pruned in fall, winter or spring, some or all of the flower buds will be cut off. It can be maintained by renewed pruning. Oak leaf hydrangea can be pruned to the shape of a small tree.
Renewal pruning of spring flowering shrubs is done by removing a quarter of the largest branches each spring so that the plant is completely renewed within four years.
Smooth hydrangea (Hydrangea arborescens), also known by old variety names such as ‘Annabelle’ and ‘Grandiflora’ and new cultivars such as ‘Invincibelle Spirit’ and ‘Incrediball’, blooms on new wood in mid- to late summer. Hydrangea (Hydrangea paniculata) blooms in late summer on new wood. Both of these hydrangeas can be pruned in fall or early winter to prevent the large flower heads from accumulating too much snow and snapping the plant in half. Smooth hydrangea varieties can be cut back clear of the ground, while clustered hydrangeas should only be cut back by a third to a half – if pruning is done at all.
They can also be pruned in winter or early spring since there are no flower buds at that time. To shorten and strengthen the stem of a hydrangea and prevent it from tipping over, pinch the tip of the stem in early summer. The plants may bloom a week or two later but will have shorter, stronger stems and are less likely to flop due to the weight of the flowers.
Some newer species of hydrangea are repeat bloomers that bloom on old wood in early summer and on new wood later in the summer. Some large-leaved hydrangeas (Hydrangea Macrophylla) also thrive on old and new wood. Do not prune these varieties until after the second flowering period. Cutting them down in winter or spring will remove some of the flower buds as the old wood is cut.
I have a detailed video on pruning hydrangeas on the Greener View YouTube channel. It’s the 16th video in the Pruning Chapter #10 playlist that matches the Pruning chapter in the Greener View Gardening book. Go to greenerview.com for links to videos and to book.
Email questions to Jeff Rugg at (email protected). To learn more about Jeff Rugg and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.