When to cut back hydrangeas: An easy-to-follow guide

Figuring out when to cut back hydrangeas is so confusing for new gardeners and homeowners! Heck, it’s even confusing for long-time gardeners. Most articles offer information about hydrangea pruning solely based on the plant’s species or by whether it blooms on “old wood” or “new wood”. But what does all of that mean? Isn’t there an easier way to determine when to cut back different hydrangeas? Yes! In this article, I share a very simple way to determine the best pruning time based on the shape and color of the blooms, even if you don’t know what species your hydrangea is.

Why pruning time matters for hydrangeas

As a professional horticulturist who hosted a live call-in radio show for 15 years, “When do I prune my hydrangea?” is among the most commonly asked gardening questions. This is because if you prune hydrangeas at the wrong time, you might accidentally cut off all the dormant flower buds. This could mean fewer blooms or even no blooms at all. Because the flowering potential of these shrubs is influenced by pruning, learning when to cut back hydrangeas is a popular concern.

Different types of hydrangeas = different pruning times

All hydrangeas bloom in the summer, but not all hydrangea types produce their flower buds at the same time. This is why pruning time matters so much. Let me explain.

• Some hydrangea species make new flower buds in the spring, just a few weeks before those buds open into gorgeous flowers. (Flowering on the current season’s growth like this is called blooming on “new wood.”)
• Other types of hydrangeas make their new flower buds in the late summer or fall, a full 9+ months before they open into blooms. Those buds stay dormant in the brown stems all winter long and then open the following summer to produce the next year’s flowers. (This is called blooming on “old wood.”)
• A small number of hydrangeas – mostly popular varieties and cultivars like the ‘Endless Summer’ collection and ‘Blushing Bride’ – produce flower buds both in the spring and in the fall. (This means they bloom on both “new wood” and “old wood.”)

You might already be able to deduce how a poorly timed pruning job can impact bud production and flowering. Cutting off stems that are holding dormant buds means you are cutting off all your flowers for the coming summer.

Is this confusing? You bet! So, how do you keep everything straight and choose a best time to prune? My trick: prune by flower shape and color, not by species name or by the “old wood/new wood” designation. Pruning by flower type is much, much easier and way less confusing than pruning by the species, especially for new gardeners.

The ease of pruning by flower types

Regardless of whether the new buds are produced in spring or fall, if you learn how to prune hydrangeas by their flower shape and color, you’ll always have success. Each of the following sections covers how and when to cut back hydrangeas based on what their blooms look like.

When to cut back hydrangeas that produce pink or blue flowers

If your hydrangea shrub has a flower head that is big and round and in shades of pinks and blues, it fits into this category. These classic hydrangeas are known as mophead or bigleaf hydrangeas (Hydrangea macrophylla).

If you have this type of hydrangea, the best time to cut it back is in the mid spring. Here are some pointers:

1. Yes, you need to leave the brown sticks on the plant all winter long. They may look dead, but they are not. They are holding dormant buds that will produce flowers in the coming summer.
2. Do not prune in the fall, winter, or early spring.
3. When the danger of frost has passed in your growing zone and it is mid spring, it’s time to prune these hydrangeas.
4. To prune, in mid spring follow each brown stem down from its tip until you see signs of new growth. What you’ll typically see is new green buds emerging from the side of each brown stick. Use a pair of sharp pruners to cut the stick off just above the upper-most green bud. On some stems, the new growth may be close to the top, while on other stems it may be closer to the bottom.

Also in this category are hydrangeas with lace-like flowers, known as lacecap hydrangeas (Hydrangea serrata and Hydrangea aspera). It’s easy to remember they are in this category because they also produce flowers that are shades of pinks and blues.

When to cut back hydrangeas that produce a ball of white or green blooms

If your hydrangea flowers look like big round balls of white or lime green blooms (or very occasionally pink), it fits into this category. These types of hydrangeas are known as the smooth hydrangea (Hydrangea arborescens). Popular varieties include ‘Annabelle’ and ‘Incrediball’. There are even a few pink varieties such as ‘Invincibelle Spirit’.

If you have this type of hydrangea, the best time to cut it back is in the late winter or early spring. Here are some pointers:

1. You really can’t mess up the pruning of these hydrangeas. While early spring pruning is recommended, if you prune in the fall, it’s not the end of the world.
2. Do not prune in late spring or summer. If you do, you will be cutting off the buds before they open.
3. In late winter or early spring (I opt for March in my Zone 5 Pennsylvania garden), cut the plant back to between one-quarter and one-half of its total height. Just use a pair of pruners or long-bladed hedge clippers and chop it back. Easy cheesy. Some gardeners even opt to cut it all the way back down to the ground.
4. The white flowers are produced on the current year’s growth. You cut all the stems back and the plant generates all new growth and new flower buds that will open a few weeks later.

When to cut back hydrangeas with cone-shaped flowers

If your hydrangea makes elongated cone-shaped blooms that are white, pink, or deep pink, you have a hydrangea in a group known as the panicle hydrangeas (Hydrangea paniculata). Popular varieties include ‘Limelight’, ‘Bobo’, and ‘Flare’.

If you have this type of hydrangea, the best time to prune is in the early spring. Here are some tips for cutting back panicle hydrangeas:

1. The cone blooms are produced on new growth so you should prune in early spring, just before new growth occurs. I time my pruning to around the last expected spring frost. Cut the entire plant back by about a third of its total height.
2. Do not prune in late spring or early summer, after the buds have already set.
3. You don’t need to prune these plants at all if you don’t want to. The plants bloom prolifically regardless.
4. If the plant is becoming overgrown, you can cut it all the way back down to the ground in the late winter or early spring. It will still generate summertime blooms. These are very easy plants.

When to cut back hydrangeas with oak-leaf shaped foliage

If your hydrangea has oak-leaf shaped foliage and produces large white cone-shaped blooms, it’s among the oakleaf hydrangeas (Hydrangea quercifolia). The leaves of these woody hydrangeas are uniquely shaped and turn a beautiful red color in September through November.

If you have this type of hydrangea, the best time to prune is never. The second best time is right after the flowers fade in summer. Here’s some advice on how to do it right:

1. Oakleaf hydrangeas hold their buds in their stems all winter long. Prune lightly and only in summer.
2. Do not prune in fall, winter, or spring or you will be cutting off the flower buds
3. I recommend not pruning these hydrangeas at all. They have such a lovely form without pruning so it really isn’t necessary.

Following the rules

As you can see, knowing when to cut back hydrangeas is important for both plant health and bloom production. Following the easy rules outlined above is a great way to ensure many successful and beautiful hydrangea seasons to come.

For more on growing beautiful hydrangea, please visit these articles:

• How to protect hydrangea over the winter
• Fall care for hydrangeas
• Funky hydrangea varieties
• When to plant hydrangeas
• Hydrangeas and deer

Pin this article to your Landscaping board for future reference.