To reduce the size of a hydrangea that blooms on new wood, cut off about one-third of each stem in late fall or early spring before it begins to leaf out. If your hydrangea blooms on old wood, prune right after it has bloomed when the flowers are fading.
In late winter or early spring, these shrubs can be cut all the way back to the ground. Smooth hydrangeas will produce much larger blooms if pruned hard like this each year, but many gardeners opt for smaller blooms on sturdier stems.
Prune fall blooming hydrangeas, or old wood bloomers, after they bloom in the summer. If you prune old wooded hydrangeas in fall, you are cutting off next seasons blooms. Summer blooming hydrangeas, or those that bloom on new wood, are pruned in the fall, after they stop blooming.
Cut back any clearly dead branches, which are brittle and snap off easily. This can be done in the fall or any time you see a dead branch. To reduce the size of a hydrangea that blooms on new wood, cut off about one-third of each stem in late fall or early spring before it begins to leaf out.
Hydrangeas that bloom on new wood can be safely pruned in late fall once the plants have gone dormant or in early spring. Next year's flower buds won't be formed until late spring the same year they bloom, so there is no risk of removing the buds if you prune in fall or spring.
Hydrangeas do not require strict reqular pruning; simply keep them healthy by removing dead wood and they will grow and flower well.
Wrap with winter protection.
During the winter, make a DIY A-frame wire cage out of burlap and chicken wire to protect your hydrangea plant. This cage will protect it from winter winds, heavy snowfall, and cold temperatures.
While some plants bloom on new growth, others primarily set flower buds on old wood. Regardless, it is best to wait to prune all hydrangeas until spring. In the fall, hydrangeas (and all trees and shrubs) are in the process of going dormant. They do not produce very much new growth until the following spring.
Mophead hydrangeas look lovely in the fall when their blue, purple and pink flowers contrast with the fall foliage. Brown flowers can be snipped off if they annoy you, but you don't have to remove them. Look for flowers like this to dry or for making Hydrangea Wreaths.
Regardless of the type of hydrangeas you're growing—and whether it blooms on old or new wood—the cutting process is the same. Start by using clean, sharp shears, then make your cut. "Cut stems above a node, and include at least two leaf groups on the cut stem," says Godshalk.
To rejuvenate the hydrangea, remove up to 1/3 of the older living stems down to the ground each summer. This will revitalize the plant. If necessary to control the size of the plant, cut back before late July to allow for buds to develop. Usually the plant will return immediately to its former size.
Big Leaf Hydrangeas, Hydrangea maculata, do not tolerate frosts well and should be covered to prevent leaf damage and flower loss.
The reason that climbing hydrangeas are pruned in summer is because the flowers are produced on the previous year's wood. If they are pruned earlier in spring, before flowering, the blooms for that year will be sacrificed.
A popular cultivar of the repeat bloomers is 'Endless Summer' but there are many newer repeat blooming cultivars available in the trade. Sometimes bigleaf hydrangeas become overgrown and need to be trimmed. However, too much pruning will greatly reduce or eliminate flowering.
For example, when you might prune a 'Snowball' hydrangea differs from when you should cut back 'Endless Summer' hydrangea. If you prune them at the wrong time, you could risk cutting off all the flower buds and ending up with no blooms that year. Here's what you need to know about properly pruning your hydrangeas.
Without going through the deadheading process, hydrangeas will not produce as many flowers and the few produced may not grow as big to their full potential.
Old Wood Bloomers
Hydrangeas that bloom on old wood do not need pruning and are better off for it.
During the winter months, most of the blooms fall from the plant and whatever is left often turns dry and brown. The cold winter weather can leave the remaining foliage and buds of hydrangeas dead and damaged - but what's the most likely cause?
Snow cover not only provides insulation, but also a water source. If you live in an area that doesn't have snow — or doesn't get snow — make sure you've got enough rain or water to get them through. Also, be sure the base of the hydrangea is covered with wood chips, oak leaves, pine straw or other mulch.
Some introductions such as the Forever and Ever series or the well known Endless Summer family bloom both on old wood and new wood. The spring flowers occur on the prior year's old wood, while the fall flowers occur on the plant's current-season new-wood growth.