How To Prune Hydrangeas That Grow On Old Wood

Pruning hydrangeas that grow on old wood is all about timing and knowing exactly which stems to cut.

If you prune these varieties at the wrong time, you’ll accidentally remove the flower buds that are already set for the coming season.

These hydrangeas form their buds in late summer on the growth from that same year, and that growth becomes the “old wood” that blooms the next spring.

So when you know how to prune hydrangeas that grow on old wood, you can keep them full, healthy, and loaded with those big, beautiful blooms.

In this post, we’ll break down the simple rules for pruning these specific hydrangeas, the mistakes to avoid, and how to handle dead or damaged stems.

Let’s dig in.

How to Prune Hydrangeas That Grow on Old Wood

The secret to pruning hydrangeas that grow on old wood is to do it right after they finish blooming in mid-summer.

If you prune them in fall, winter, or early spring, you’re cutting off the buds that formed last year, and that means no flowers for you this year.

So the best approach is to tidy them up immediately after the flowers fade.

Here’s the simple method:

1. Wait Until Flowers Fade in Summer

The moment your hydrangea’s blooms start to turn brown and crispy, that’s your window.

Pruning hydrangeas that grow on old wood should happen while the plant is still actively growing, but after the flowering show is over.

This gives the plant plenty of time to produce new stems and set buds for next year.

If you wait until late fall, it’s already too late because the buds are sitting there waiting for spring.

2. Cut Just Above a Pair of Healthy Buds

When you’re pruning hydrangeas that grow on old wood, always make your cuts just above a pair of fat, healthy leaf buds.

Look for buds that are plump and green, not dry or shriveled.

Make a clean cut at a 45-degree angle, about a quarter inch above those buds.

This encourages the plant to branch out from that point, which fills in the shrub nicely.

3. Remove Only One-Third of the Stems

A light trim is all you need for most old wood hydrangeas.

Remove about one-third of the oldest stems right down to the base of the plant.

These are the thick, woody, sometimes gnarly stems that have been around for several years.

Cutting them to the ground stimulates fresh, vigorous growth from the roots.

But don’t go overboard because the remaining old wood is what’s going to bloom next season.

4. Deadhead Spent Blooms Without Cutting Deep

If you just want to clean up the plant, you can simply deadhead the spent flower heads.

For pruning hydrangeas that grow on old wood, deadheading means snipping the old bloom stem back to the first set of healthy leaves.

This removes the ugly brown flowers without disturbing the buds lower down on the stem.

It’s the safest way to tidy up if you’re unsure whether a stem is going to bloom again.

Which Hydrangeas Grow on Old Wood?

Before you grab your pruners, it’s super important to know which hydrangeas are old wood bloomers.

Not all hydrangeas are the same, and following this guide for the wrong type will leave you with no flowers.

Pruning hydrangeas that grow on old wood is the right move for these popular varieties:

1. Bigleaf Hydrangeas (Hydrangea macrophylla)

These are the classic pink and blue mophead or lacecap hydrangeas.

They form their flower buds on old wood, so they’re the most common type people worry about pruning.

If you prune them in spring, you’re cutting away the very buds that would’ve given you those huge, colorful blooms.

2. Oakleaf Hydrangeas (Hydrangea quercifolia)

Oakleaf hydrangeas are easy to spot because of their large, lobed leaves that look like oak tree leaves.

They also bloom on old wood, producing long, cone-shaped white flower clusters.

They’re super tolerant of pruning, but the same timing rules apply here.

3. Climbing Hydrangeas (Hydrangea anomala petiolaris)

If you have a climbing hydrangea covering a trellis or wall, it also blooms on old wood.

These vines need very little pruning, and when you do prune hydrangeas that grow on old wood, you’re just keeping them in bounds.

Cut back wayward shoots right after they flower, but otherwise leave them alone.

What Happens If You Prune at the Wrong Time?

So you’re now wondering what happens if you accidentally prune hydrangeas that grow on old wood at the wrong time.

The main consequence is you’ll lose a season of flowers.

But the plant itself won’t die.

It will focus all its energy on producing leaves and new growth for the rest of the year.

And then, with any luck, it will set buds for next year if it has enough time before the first frost.

The real danger is pruning too late in the season because the new growth might not harden off before winter.

That soft new growth can get zapped by freezing temperatures.

1. You Cut Off the Flower Buds

The biggest reason to master pruning hydrangeas that grow on old wood is that the buds are already formed by late summer.

When you cut stems in spring, those buds go right in the compost pile.

So instead of a bush full of blooms, you get a leafy green shrub all summer long.

2. The Plant Gets Leggy and Thin

If you never prune old wood hydrangeas, they can become overcrowded with old, woody stems.

These older stems produce fewer and smaller flowers each year.

So a little annual pruning is good for the plant’s health and vigor.

How to Rejuvenate an Overgrown Old Wood Hydrangea

If you’ve neglected your hydrangea for years and it looks like a tangled mess, don’t panic.

You can still fix it, just over time, not all at once.

Rejuvenation pruning for hydrangeas that grow on old wood is done gradually over three years.

1. Remove One-Third of the Oldest Stems Each Year

In the first year, cut out the thickest, oldest stems at ground level right after flowering.

This opens up the center of the plant to light and air.

The next year, do the same to another third of the old stems.

And the year after that, finish the job with the last third.

2. Never Cut Everything to the Ground

For hydrangeas that grow on old wood, a hard “renewal prune” to the ground is a terrible idea.

That method is only for panicle and smooth hydrangeas that bloom on new wood.

If you cut an old wood hydrangea down to the ground in fall or spring, you won’t see a single flower that year.

So, How to Prune Hydrangeas That Grow on Old Wood?

To prune hydrangeas that grow on old wood, you simply wait until the flowers fade in summer.

Then you cut spent blooms back to healthy buds, remove a third of the oldest stems, and clean up any dead or damaged growth.

That’s it.

You don’t need to be fancy or aggressive with these plants.

Just remember this golden rule: if it blooms early in the season, it’s almost certainly blooming on old wood.

So if you want to prune hydrangeas that grow on old wood successfully, always time your cuts for mid-summer.

Do that, and your hydrangeas will reward you with a spectacular display of color every single year.

Happy pruning.