By Susan Martin for Proven Winners
Photographs courtesy of Proven Winners
Itching to prune your hydrangeas this fall? Wait! Read this article first to avoid accidentally pruning off next year’s blooms. We’ll show you which types of hydrangeas can be pruned safely now in three simple steps.
Step 1: Identify which type of hydrangea you are growing
Most shrub-form hydrangeas sold in North America are one of five types: bigleaf, mountain, smooth, panicle and oakleaf. Some form their flower buds on old wood, meaning next year’s buds are already present on the branches in fall and winter. Others form their flower buds on new wood once they begin to grow in spring.
Since it is only safe to prune hydrangeas that bloom on new wood in the fall without the risk of sacrificing next year’s flowers, it is important to identify which type of hydrangea you have before you prune.
Stop to watch this video which will help you easily identify your hydrangea. You can read even more about it in this detailed article about pruning hydrangeas.
Step 2: Decide when to prune
Once you have completed step one, you will know which type of hydrangea you are growing. Then, follow this guide to decide when to prune.
You can see next summer’s flower buds are already formed in October on this oakleaf hydrangea. Pruning it in fall would remove those buds so it would not bloom next year.
Pruning Hydrangeas that Bloom on Old Wood
Most shrubs that bloom on old wood should be pruned immediately after they are done flowering. However,in most climates, hydrangeas that bloom on old wood finish flowering so late in the season that pruning them after they bloom doesn’t leave enough time for them to regrow and form flower buds for next year. That’s why we suggest that you avoid pruning this type of hydrangea except to remove any completely dead branches in the spring once the plant starts to leaf out.
Since panicle hydrangeas like Fire Light® bloom on new wood, they can be pruned safely in late fall without removing any of next year’s flower buds.
Pruning Hydrangeas that Bloom on New Wood
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.
Let’s Dance® Rhythmic Blue® bigleaf hydrangea reblooms reliably and requires little to no pruning except to remove any dead branches in the spring.
Pruning Reblooming Hydrangeas
Reblooming hydrangeas produce flowers on both old and new wood. That makes it tough to find a good time to prune them without sacrificing some flowers. Reblooming cultivars should be pruned the same way as hydrangeas that bloom on old wood, meaning you should only need to prune out a few (if any) dead branches in the spring once the plant starts to leaf out.
Generally, it is safe to prune as much as one-third off of your hydrangea that blooms on new wood. For example, if it is six feet tall, it’s safe to prune as much as two feet off the top and sides. We do not recommend pruning more drastically for two reasons:
Pruning it further removes too much of the sturdy framework that keeps the plant standing upright.
The plant needs to retain enough foliage to make an adequate amount of food to support the root system.
When you prune, make your cut just above a set of large, healthy leaves. If a branch is broken or dead, it can be removed completely. If in doubt, don’t prune! No hydrangea requires pruning to grow and bloom well.
My hydrangea is too big!
One common misconception about hydrangeas is that you can prune them throughout the season to keep them shorter. Pruning your hydrangeas to reduce their height isn’t effective because they will grow right back to their original size, or even larger because the act of pruning stimulates new growth. Instead, transplant your too-large, still-dormant hydrangea to a new spot in early spring and replace it with a variety that naturally stays shorter.