So how do you know when to prune hydrangeas? That is a question that shouldn’t be answered without a follow up question or two. The answer is pretty easy if you know the variety or type of hydrangea you have, but when you don’t things can get quite confusing. For homeowners who inherited their landscape and those of us who buy and throw the tag away and years later decide our aging hydrangea needs a little work we need a little extra guidance to get to the correct answer. Get started on the right foot by checking out our huge selection of Hydrangeas from our online nursery.
When To Prune Hydrangeas
Understanding New Wood Versus Old Wood
New wood is growth that has occurred during the current season. Stems that have been on the bush since the summer before the current season are considered old wood. The buds of old wood hydrangeas form in summer or fall shortly after the flowers have faded.
Old wood hydrangeas bloom earlier in the season usually in late spring or early summer and tend to be done flowering by midsummer. The branches that you see the blooms on tend to be more woody and brown.
New wood bloomers bloom on young green branches and tend to start flowering in midsummer and bloom until frost.
Identifying Hydrangeas that Bloom on Old Wood
Big Leaf, Mophead, Lacecap Hydrangeas (H. macrophylla)
If the hydrangea in your backyard has heart-shaped, thick, shiny foliage with serrated edges, then you have H. macrophylla. The leaves are significantly more textured than a smooth hydrangea.
Oakleaf Hydrangea (H. quercifolia)
The oakleaf is easy to distinguish. The stems are woody, and the leaves are shaped like an oak leaf. Cone shaped flower heads is another feature of this group.
Identifying Hydrangeas that Bloom on New Wood
Smooth Hydrangeas (H. arborescens)
While the leaves are heart-shaped like big leaf hydrangeas, the leaves of smooth hydrangeas are thinner, matte-looking, and not as crisp as those of the big leaf. The blooms are large and round and made up of tiny individual flowers. The flowers of smooth hydrangeas are green when they first open. They turn white and remain that way for 2 to 3 weeks before fading back to green.
Panicle Hydrangeas (H. paniculata)
This type of hydrangea has cone shaped flowers with long stems. The foliage is similar to smooth hydrangeas.
Identifying Hydrangeas That
Bloom On Both New & Old Wood
Just to make things a little more complicated there are newer cultivars of H. macrophylla that bloom on both new and old wood. These bushes look similar to the type that grows on old wood as described above, but they are rebloomers that have a very long stretch of bloom time. These hydrangeas usually flower in spring, summer, and fall.
Pruning By Type: When and How
Pruning By Type: When and How
Pruning Old Wood Hydrangeas
Prune H. macrophylla (Big Leaf, Mophead, Lacecap) in summer or early fall when the blooms are spent. The Farmers Almanac and many other resources recommend pruning old wood hydrangeas prior to August 1st to be sure you don’t remove forming buds. Remove up to ⅓ of the stems each year. Remove the weakest old and new shoots by pruning them at the ground or back to the main trunk.
Oakleaf hydrangeas do not require pruning. Trim them up lightly for shape after they are done flowering.
Pruning New Wood Hydrangeas
Smooth hydrangeas like a heavy hand. These varieties can be pruned all the way back to the ground in winter or early spring while still dormant prior to new growth emerging. If you are already seeing new green growth you haven’t necessarily lost your chance to tune up your plant. It can actually be a great way to know what wood is no longer alive or productive. Prune back any brown stems or branches that have no new growth on them. Often new growth only comes from the roots. If this is the case carefully prune out all the old stems avoiding the fresh young growth.
Panicle hydrangeas don’t need pruned every year, but if they are overgrown or have a hard time holding up their blooms during the growing season prune the entire bush back ¼ to ½ during dormancy.
Pro Tip - Deadheading
You can deadhead any hydrangea variety anytime. Although this isn’t necessary it creates a cleaner look and can help encourage reblooming. Trim the stem back to right above the first set of leaves below the bloom. Be sure to use clean, professional pruners for best results.