How to Prune Hydrangeas in Late Winter (No Matter What Type You Have)

Which phrase rings more memorable to you?

Old French climbing rough mountain oak.

Old rough French climbing mountain oak.

No, it doesn’t make much sense. And no, I didn’t lose my mind just yet. Although, with January and February dragging on for a combined 138 days, none of which was sunny or warm enough for a bit of gardening, I might be cutting it close.

By late winter, my skin and my soul are as dry as this hydrangea.

The two phrases above are a mnemonic device I came up with to remember which hydrangeas bloom on old wood. Though, I could not make up my mind whether it was the Frenchie that was rough or the mountain. So I present to you both versions and let you decide how you wish to remember this detail.

Here’s a breakdown of the phrase. It will make more sense once it clicks, I promise.

Old = a hydrangea that blooms on old wood

French hydrangea (Hydrangea macrophylla)

Climbing hydrangea (H. petiolaris)

Rough leaf hydrangea (H. aspera)

Mountain hydrangea (H. serrata)

Oak leaf hydrangea (H. quercifolia)

Prune it at the wrong time, and you might as well say goodbye to summer blooms.

But why should we even bother to learn which type of hydrangea blooms on old or new wood?

Simple. This detail will come in very handy when deciding whether to prune said hydrangea in spring. And it will also be an indication of how hard we can prune it.

In a nutshell, we can prune old wood hydrangeas in late spring and early summer, but we should only give them a light prune, never a hard prune (down to the ground, for example).

Why is that?

On old wood hydrangeas, this year’s blooms have already grown out last year.

Because blooming on old wood means that this year’s buds (both leaf buds and flower buds) have already formed on last year’s canes, so if we hard prune now, we’re removing the flowers that would open up this year.

You can take a screenshot of this formula for late winter or early spring pruning hydrangeas:

Old wood = light pruning (mostly deadheading and clean-up)

New wood = harder prune (when necessary)

The dry flowers served as insulation over the winter. But it’s time to remove them and make room for new growth.

So that means there are some hydrangeas that bloom on new wood, right?

Correct! The most common ones are smooth-leaf hydrangea (Hydrangea arborescens) and panicle hydrangea (H. paniculata). We’ll talk about them later.

How do I know which hydrangea I have in my garden?

I know it gets a bit tricky, especially if the plant doesn’t come with any labels or if we’re buying cultivars that may stray a bit from the norm. Here’s a quick look at how to tell which hydrangea you have. And yes, we are following the order in the mnemonic phrase.

1. French hydrangea (Hydrangea macrophylla)

This is probably the one you have in your garden. End of article.

Probably what we’re all thinking of when we hear the word ‘hydrangea.’

Just kidding! But I think this is the most popular type of hydrangea in the United States. You can recognize it by its signature mophead blooms that come in shades of pink, blue or purple.

Did you know that you can change the color of the flowers just by playing with the acidity (pH) of the soil? I wrote about it in this article.

You should deadhead French hydrangea in late winter or early spring by trimming it at an angle right above the first bud – the one right below the spent blooms.

Trim right below the dead flowers, but right above a bud.

And while you’re at it, you can remove the canes that don’t have any buds on them. Try to bend the stems just a little bit using your thumb. If they’re flexible and you feel a bit of resistance, then the canes still have live tissue in them. If they’re brittle and snap, just trim them at ground level.

This cane was completely dead. So I prune it at ground level.

2. Climbing hydrangea (H. petiolaris)

If I could only pick one type of hydrangea to grow, I would always pick a climbing hydrangea. I know I’m flirting with controversy of the lowest stake here, but give me a green wall over a mass of colorful mop heads any time of the year. Plus, this type of hydrangea brings so many pollinators to my yard. It’s an absolute joy to watch and listen to the buzz from April to June.

This climbing hydrangea is growing on a fence in my backyard.

I’m growing two mature Hydrangea petiolaris, one on a trellis attached to the front of my house and the second one against a fence in my backyard. They’re both around nine feet tall (around 2.70 meters), so pruning them in early spring turns into quite an event.

Since this is a climbing hydrangea, make sure you’re comfortable with using a step stool or delegating the task to a tall member of your household.

It takes a while to prune it in late winter, but it’s totally worth it.

Start by cutting off the dry flowerheads, but don’t let them go to waste. They make excellent brown matter, and because they keep their shape so well, they help with aeration in the compost bin.

You can also saw off some of the stems that may be crisscrossing, but don’t take off too much if you want a full plant come summer.

I brought “a few” dry flower heads indoors.

I wrote an entire article describing the best way to prune a climbing hydrangea. Have a read here.

3. Rough leaf hydrangea (H. aspera)

Even though it shares a color palette with French hydrangea, you can easily tell these two apart. First of all, the leaves of the Frenchie are smooth and glossy, while Hydrangea aspera has fuzzy, velvety leaves. The flowers of the latter are not mopheads, but large lacecaps that reach peak growth in the summer.

Fuzzy leaves are the telltale sign of *Hydrangea aspera*.

Since this type of hydrangea is native to Asia, where it grows as a woodland plant, you’ll notice it will get larger much faster than the macrophylla. A single shrub can reach between 10 to 12 feet tall (over 3 meters) and spread around 8 to 10 feet (2.5 to 3 meters).

This is also an old-wood hydrangea, so prune it as such. Remove the lacecap stems right above the first bud. And since rough leaf hydrangea is such a robust grower, you can trim a couple of the older canes down to the ground in the spring, especially if it’s overgrowing its current location.

4. Mountain hydrangea (H. serrata)

You don’t have to live in the mountains to grow mountain hydrangeas. This type gets its nickname due to its native habitat in the mountainous areas of Japan and Korea. I’ve read that the leaves are used for making herbal tea infusions, but I have yet to try it myself.

Mountain hydrangea has large lace cap blooms.

The edges of the leaves are serrated (hence the Latin name) and the flowers look like lacecaps. Due to its natural habitat, this type of hydrangea does really well in part shade. Just like with French hydrangeas, the curious gardener can experiment with the acidity of the soil in order to alter the color of the blooms.

Mountain hydrangea is an old wood perennial, so this year’s flower buds have already set last year. It only needs light pruning to remove dry flowerheads and any stems that may have been damaged over the winter months.

Always prune below the flower but above a bud.

5. Oak leaf hydrangea (H. quercifolia)

It’s so easy to tell apart oak leaf hydrangeas, a southeastern United States native plant, from any other type. Its leaves look very similar to oak leaves. I know, it’s not much of a surprise, given its name.

And if you’re still not sure, try to recall the color of its foliage in the fall. If it was a mix of fiery red and golden rust and showstopper orange with a dash of purple, then you got yourself a Hydrangea quercifolia adorning your garden.

Have a look at those leaves. Oak hydrangea is the only type of hydrangea with these leaves.

The cone-shaped white flowers have a very pleasant scent. But don’t try to identify it by the shape of the flower heads, since it has this in common with Hydrangea paniculata (Panicle hydrangea) which blooms on new wood and can handle a hard prune in early spring.

Just like the rough-leaf type, this hydrangea also grows pretty large. It can reach up to 12 feet in height (3.60 meters) although there are some cultivars that stay around 5 feet tall (1.5 meters).

Stick to doing just minimal pruning in late winter. Remove the old dry flowers and trim down any dead or diseased stems. If you want to shape it or contain it a bit better, you should wait until it’s done blooming in late summer.

Are there any hydrangeas that need a hard prune in late winter?

Yes, I hear you! You can’t wait for an excuse to get out there and do some cleanup. There are two types of hydrangeas that could do with a harder prune this time of year.

6. Panicle hydrangea (H. paniculata)

You’ll recognize the panicle hydrangea by its lilac-shaped flower clusters. And the cool thing about them is that the flowers change color without any outside intervention needed. The clusters start out white. As the summer nears to an end and the days are getting gradually shorter and cooler, the flowers start to get a pinkish-red hue, often resulting in an ombre effect.

Panicle hydrangea flowers usually start off white, then change color over the summer.

The gorgeous panicle hydrangeas produce these blooms on new wood. This means they’ll push out flower buds for this year only after they’ve started to leaf up in spring. So if you haven’t pruned them in late fall once they went dormant, now’s another good time to do it.

If you have a young plant, keep pruning to a minimum in order to give it some time to get established and fill up. If your plant is older, you can prune away.

Deadhead it first to assess the framework you’re left with.

Start by removing the dead flower heads to assess how large your hydrangea is without all the floofs. Then take down the main stems by about a third, always cutting just above a bud.

Remove any dead stems, as well as most of the weak side growth. This type of hydrangea is not only a fast grower, but also a prolific bloomer with large heavy flower heads. It needs a strong framework to grow on, so don’t over prune it.

By the way, this is a type of hydrangea that you can successfully turn from a shrub to a tree-shape. (But slowly, over a few years.) So that is also a choice.

7. Smooth hydrangea (Hydrangea arborescens)

Unless you’re an absolute newbie to growing hydrangeas, you’ve probably heard of ‘Anabelle’ – the super popular hydrangea that produces a mass of immense poufs of white blooms all throughout summer. ‘Anabelle’ is a cultivar of Hydrangea arborescens.

‘Annabelle’ produces a mass of flowers on new wood.

Smooth hydrangea flowers on new wood (this year’s growth) starting in May and reaching its peak in late July. It prepares for this fountain of blooms by putting out a lot of new wood growth from March until May. In fact, within these couple of months it can grow up to five feet (1.5 meters).

They are incredibly beautiful even when they’re dry.

Unless we want the blooms to tower way over our heads, we need to give it a hard prune before the growth starts.

There are two ways to do this. First, we can cut it a little bit above ground level. This type of hydrangea will bounce back and give us all new growth for the season.

Cut them to a V-shaped framework as low as you want to go.

For a less drastic approach, you can prune them in layers. Here’s what I mean. Prune the exterior stems down to the ground or a leaf bud higher; then prune the next layer of stems a little bit higher, then the inside ring of stems higher still.

Overall, by the point you get to the central stems, you’re probably only taking out about a third of the height. This will space out the blooms both in time (they will open in succession) and in height.

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