How To Prune Big Leaf Hydrangeas

If you’re wondering how to prune big leaf hydrangeas, you’re not alone. It’s the most common question gardeners have about these beautiful shrubs, and getting it right is key to seeing those stunning blooms each summer.

Big leaf hydrangeas, or Hydrangea macrophylla, are the classic blue or pink mopheads and lacecaps. Their pruning needs are unique because they bloom on old wood. This means the flower buds for next summer are formed on the growth from the current year. Prune at the wrong time, and you might accidentally cut off all your future flowers. Don’t worry, though—once you know the simple rules, it’s an easy task that makes your plants healthier and more floriferous.

This guide will walk you through the entire process, from timing to tools to the final cuts. We’ll focus on the essential steps that protect next year’s blooms while keeping your plant in great shape.

Why Pruning is Different for Big Leaf Hydrangeas

Not all hydrangeas are pruned the same. Some types bloom on new wood, meaning you can cut them back in late winter and they’ll still flower that same year. Big leaf hydrangeas are different. They set their bloom buds in late summer and fall for the following year. If you prune them in fall or spring before flowering, you remove those buds. The goal is to prune just after the flowers fade, giving the plant maximum time to grow new stems and set buds for the next cycle.

When to Prune: The Golden Rule

Timing is everything. The safest and best time to prune is immediately after the flowers fade, typically in mid-to-late summer. For most regions, this is July or early August.

Do Not Prune in Fall or Winter: The dried flower heads actually provide some protection to the tender buds below them during cold months.
Do Not Prune in Spring: By spring, the buds are swelling and you will clearly see you’re cutting off the flower potential.
Exception for Damaged Wood: You can always remove dead, damaged, or diseased branches as soon as you spot them, at any time of year.

Gather Your Tools

Using the right tools makes the job cleaner and healthier for the plant. You’ll need:

Bypass Pruners (Hand Shears): For most cuts on stems up to ½ inch thick.
Loppers: For thicker, older branches, usually up to 1.5 inches.
Gardening Gloves: To protect your hands.
Rubbing Alcohol or a Disinfectant Spray: To clean your tool blades between plants and after cutting any diseased wood. This prevents spreading problems.

Make sure your tools are sharp. A clean cut heals faster than a ragged, torn one.

Step-by-Step Pruning Guide

Follow these steps in order after your hydrangea has finished its main flush of blooming.

Clean Up Dead Wood: Start by removing any completely dead stems. These will be brittle, gray, and have no green growth. Cut them all the way back to the base of the plant.
Remove the Old Flowers (Deadheading): This is the main event. For each faded flower, find the first set of large, healthy leaves below it. Make your cut about ¼ to ½ inch above that leaf node. You might see tiny buds already forming at the base of the leaf stem; that’s next year’s growth starting.
Thin Out the Plant: Look for the oldest, thickest stems. Removing a few of these each year encourages new, vigorous growth from the base. Choose up to ⅓ of the oldest stems and cut them right down to the ground.
Shape and Balance: Step back and look at the plant’s overall shape. Trim back any excessively long or awkward stems to a leaf node that faces the direction you want new growth to go. Aim for a balanced, rounded form.
Clean Up: Remove all cuttings from around the base of the plant to discourage pests and disease.

Special Cases: Rejuvenating an Old Plant

If you’ve inherited a giant, overgrown hydrangea that flowers poorly, you can take more drastic action. Over three years, you can rejuvenate it without sacrificing all blooms.

Year 1: After blooming, remove ⅓ of the oldest, thickest stems at ground level.
Year 2: Remove another ⅓ of the oldest remaining stems.
Year 3: Remove the final batch of old stems. By this point, the plant will be composed of newer, more productive wood and should be flowering much better.

What Not to Do: Common Pruning Mistakes

Avoid these errors to ensure a great bloom display.

Cutting Everything Back: Never “haircut” the entire plant back by shearing off the top. This removes all the bud-bearing stems.
Pruning Too Late: Pruning after August risks removing the buds that have already formed for next year.
Ignoring the Center: Always thin from the center to improve air circulation, which reduces disease risk.
Using Dull or Dirty Tools: This can damage stems and introduce infection.

Aftercare: What to Do Post-Pruning

A light feeding after pruning supports the new growth. Apply a balanced, slow-release fertilizer formulated for shrubs according to package directions. Then, water it in well. Continue to water your hydrangea regularly, especially if late summer is dry, as this is when it’s forming those crucial next-year buds. A layer of mulch around the base helps retain moisture and insulates the roots.

FAQ: Your Big Leaf Hydrangea Pruning Questions Answered

My hydrangea didn’t bloom at all this year. How should I prune it?

First, figure out why. It’s often winter bud kill or too much shade. In this case, prune only dead wood in spring once you can see where new growth is emerging. Avoid major pruning that summer; just deadhead any flowers if they appear. Focus on proper care and winter protection for the next season.

Can I prune my big leaf hydrangea in spring?

It’s not recommended. By spring, the buds are visible. Pruning then will definitely reduce or eliminate your blooms for the coming summer. Only remove stems that are clearly dead with no green leaves emerging.

How do I prune a lacecap hydrangea compared to a mophead?

The rules are the same—they both bloom on old wood. The deadheading technique is slightly different. For lacecaps, snip off the spent flower cluster just above the first set of leaves below it, just like with mopheads.

How far back can you cut hydrangeas?

For annual maintenance, you are only cutting back to the first set of leaves below the flower. For rejuvenation, you cut select stems all the way to the ground. Never cut all stems to the ground on a big leaf hydrangea; you’ll lose blooms for at least one season, maybe two.

Should I cut off the brown old flowers?

Yes, that’s the deadheading we recommend doing in summer. But if you miss the window, it’s fine to leave the dried flowers on over winter for protection and visual interest, then remove them in early spring before new growth fully emerges.

Pruning big leaf hydrangeas is simple once you understand their rhythm. Remember the golden rule: prune right after the flowers fade in summer. This one practice protects next years buds and encourages a strong, shapely plant. With your clean, sharp tools in hand and this guide, you can approach your hydrangeas with confidence, knowing each cut is supporting a more beautiful display for the future. The key is working with the plant’s natural cycle, not against it.