Written by davethetreecenters • January 31 How To Prune Panicle Hydrangeas – Hydrangea paniculata

Hydrangeas are among the very best of shrubs for late blooming. Not only do they flower when most other shrubs have finished for the season, but they stay in bloom for weeks and even months – and even when dead the flowers of many remain attractive. To get the best from them the first step is to realize that they are not all the same. Those mounds of big leaves, topped with large, round flowers that are often pink or blue are usually called ‘mophead’ hydrangeas, (Hydrangea macrophylla), or if prefer, ‘French’ hydrangeas. Lovely as they are, they are not especially cold-hardy, so if you live in a cold zone the hydrangeas that are easiest for you to grow are panicle hydrangeas (Hydrangea paniculata). These beauties, originally just with white blooms, but today in a much wider color-range, bloom well even in zone 3. This makes them invaluable in colder areas, but they also do well in warm and hot zones, so they can be grown just about anywhere.

To succeed with them – as with all hydrangeas – some attention to pruning is needed. Since panicle hydrangeas need very different treatment to French hydrangeas, let’s look at how to get the best from yours. Maybe you just planted one, and are wondering what comes next. Maybe you have had them for a while, or inherited some in a new garden – and they are a mess. What to do? That’s easy – here we have all the answers, so let’s get started.

What Do You Need to Prune Panicle Hydrangeas?

Don’t worry, pruning panicle hydrangeas is easy, and you don’t need anything special. It is always worth getting yourself a good pair of pruners – what some people call secateurs. There are many different brands – some good, many not – and like everything in life, you get what you pay for. Since a good pair will be your friend for decades, try to buy the best you can. There are two basic kinds. One has a blade with a straight edge that lands on the flat surface of the second blade. These anvil pruners are not so good, because even a small chip in the blade means a ragged cut that can tear the bark – not what you want. The second kind are called bypass pruners. These have a curved blade that slides beside the second blade. Most gardeners find these better. They cut cleaner and they cut bigger branches, so if you are in the market for a new pair – or don’t have a pair yet – then I recommend bypass pruners over anvil every time.

I don’t have any links to benefit from, but I do suggest if you can stretch to it, buying a pair of Felco brand. Available in right and left-hand models, with sizes to fit different hands, these are the professional’s pruner, with replaceable blades, and easy to sharpen and adjust as needed, so you always get the perfect cut.

Hydrangeas have soft stems, so pruners will usually do the job perfectly, and you won’t need anything else. If you have a very large, old bush to do, you might find a pair of bypass long-handle loppers a great help. To round out your gear and make you really to prune anything, a folding pruning saw is the third piece of equipment that is indispensable, although you will only need it on a big old panicle hydrangea. Folding protects the blade from damage, and protects you from accidents when carrying it. Again, invest in something good – Japan makes some great ones, but since they are hard to sharpen – best left to a pro – some gardeners treat them as more throw-away, so you don’t have to overdo it on price – unless you have access to a good, professional sharpener.

When Should I Prune my Panicle Hydrangea?

Since they flower in summer, the time to prune Panicle Hydrangeas is spring. This can be anytime before new shoots start to appear, or when the buds are just opening, or ‘breaking’. If you are a newbie, waiting until the buds show a little green is a good idea, as it will show you exactly what is dead or alive, and where to cut. After a while you will learn that without needing to see buds. It’s important not to cut these plants at any other time, and especially NOT to trim new branches that have leaves on them.

Panicle Hydrangeas flower on ‘new wood’, which is why they are successful in cold areas – flower buds don’t need to go through the winter, with the risk of being killed by cold.

First Thoughts

Besides pruning for flowers, we prune all shrubs for shape – and Panicle Hydrangeas are no exception. There are two basic ways you can go with the overall form of your bush. You can keep it low to the ground, with lots of branches coming from the bottom, or you can prune it taller, with just a few (2, 3 or 4) main branches of some length, and then the main growth on the top. Which you choose depends on what you want. Do you have other shrubs in front? Then go for a taller form. Are they in the foreground of a bed? Prune shorter. You get the idea.

[You might also have seen these plants also growing on a thick, single trunk. Called a ‘standard’, you can create this yourself by choosing just one big stem and cutting out the rest, but it is best, of you want this form, to get it ready-made from the pros.]

The cuts you are going to make will be of two kinds. Some will be removing branches completely, cutting them more-or-less flush with the stem they were growing from – don’t leave short stumps that just die and let in diseases. The second will be a cut straight across a young stem directly above a pair of buds. Since the buds of panicle hydrangea come in pairs along the stems, you won’t do any of the sloping cuts you might have learned for pruning roses, for example. Make a clean, flat cut that leaves the buds untouched, but doesn’t leave a piece of stem above those buds. These pairs of buds are what will send out a shoot in spring and early summer, that will end in a cluster of flowers. Young stems are the ones made last year, and you can identify them by their smoother bark, of a lighter shade of brown.

The Really Important Bit

So here is the key thing about pruning panicle hydrangeas. Since they bloom on new wood, how many flower clusters you get depends on how many new shoots there are. But. . .the more shoots there are, the smaller those clusters will be. So the key thing to remember when pruning this shrub is: –

If you leave just a couple of inches of a stem made last year, so there are just 2 or 4 buds, you will have the smallest number of stems and flowers, but those heads will be big, and appear later in the season. These can mean they are more likely to flop and even snap in heavy rain or storms.

If you cut a few inches off a stem made last year, removing just the old flower head back to the first pair of healthy buds, the plants will flower early, with smaller heads, but there will be many of them.

If you cut the stem back to leave 4 or 6 buds, then flowering will be mid-season, with lots of moderate-sized flower heads, less likely to bend over.

You decide what suits you best. Some people love to see really big heads on panicle hydrangeas, but for general landscaping, that ‘middle-cut’ is ideal.

The Steps of Pruning a Young Panicle Hydrangea

New, young bushes need some special attention to develop a strong, permanent framework, making a bush that flowers well every year, and is strong and balanced. The first thing to do is to remove all scrawny stems crowding the plant, leaving just the main stems you want. If you plant is new and young, that could be all you do the first spring – cut back to 3 or 4 strong sticks. It is worth being ruthless the first couple of years – you are laying the groundwork for a good plant, and you won’t regret this at all.

Once you have clean out to leave those main stems, take a look at what is left. If it is all weak and scrawny, remove it, and let the mains stems send out new growth. If it is stronger, then you can build a second level of branches, until, after a few years, you have the framework you want. From then on you can prune the branches from the previous year as mentioned earlier, and you will have a great plant, packed with blooms, every year.

Comments 10 comments

July 29, 2023 by Stefan

Hi,
I have been pruning my hydrangeas (limelight) for 4 or so years now, trying slightly different methods every year. But each year I get the same result. The new growth is so fast and tall it looks like a bunch of long necked ostriches poking their fat heads out of a smaller bush. All I see are 3 foot stems with a flower on each. Can I prune it twice in spring, after the race to the sky but before I see flowers starting to bud to create a nicer shape?
I wish I could send a pic.
Please help!

July 29, 2023 by davethetreecenter

It sounds like you are always pruning too hard for what you want. Can you see the difference on your plant between bark of stems that grew the year before (those 3-foot ones) and older branches? The new bark is smooth and more tan colored. Once you can see this, you are on your way. the more of that you cut off, the more you will get the ‘problem’ you describe (not a problem to everyone). Here is the key part of this blog:

If you leave just a couple of inches of a stem made last year, so there are just 2 or 4 buds, you will have the smallest number of stems and flowers, but those heads will be big, and appear later in the season. These can mean they are more likely to flop and even snap in heavy rain or storms.

If you cut a few inches off a stem made last year, removing just the old flower head back to the first pair of healthy buds, the plants will flower early, with smaller heads, but there will be many of them.

If you cut the stem back to leave 4 or 6 buds, then flowering will be mid-season, with lots of moderate-sized flower heads, less likely to bend over.

There is a more recent blog on this, which perhaps gives more detail.

Although pruning is the key element, there are other things that can contribute. Growing in too much shade will cause stems to lengthen. Too much water and nutrients. Do you have irrigation? Perhaps there is lots of water – try reducing it a bit. Too much fertilizer – cut back or leave out completely.
As for summer pruning, cutting back the new shoots, I have never done this, but it should work. You can remove the tip of a leafy stem that has started to grow. This is called ‘pinching out’, and generally will cause extra, shorter branches to form, increasing the number of blooms on shorter stems. Don’t do it after June 1 – again, I haven’t seen this work on panicle hydrangeas, but it should in theory. Why not try a part of your bush next year, not the whole thing, and see what happens – that way you won’t lose blooming completely if it doesn’t work.
I should also add that young plants, in rich soils and good conditions, can just be so vigorous this will happen no matter how you prune – they settle down, which yours should be doing by now.

September 17, 2023 by Louisa

My bush was not pruned in spring as I was out of the country. Now there are so many blooms it’s bending th branches and I know if I leave it all winter wind and snow will snap the branches. What shall I do?

September 17, 2023 by davethetreecenter

I know that the dead blooms are an attractive feature during fall and winter, but this year you are going to have to give them up. Right now they are probably coloring, pink or red, but soon they will start browning. Once that happens and they are past their best, simply cut them, and a short section of stem, off. Now you have nothing to be damaged by storms and you can return to normal spring pruning next year.

September 23, 2023 by Leigh Ann

Hello, I am new to hydrangea care…..one thing I’m totally confused about is Old Wood versus New Wood…..just when I thought I understood, I read that Panicles are New Wood. How are they New Wood? When they grow off the same bottom wood? I know that smooth hydrangeas are New Wood and that makes sense to me as everything dies back and up from the ground again. Or no? Please help me to understand.

September 24, 2023 by davethetreecenter

Yes, it is slightly confusing terminology, but easy enough once you get it.

New wood is wood that has grown in the current season. It came from buds that sprouted in spring, grew, and then developed flowers (typically) on the end of the stem. It doesn’t matter if it came from ground level or even below ground, as you point out happens with smooth hydrangea, or if it comes from existing branches of previous years – it’s still all ‘new wood’.

Now at this point you are probably about to say that in that case all flowers are on ‘new wood’, because in spring new leaves appear on, say, a mophead hydrangea and then a flower comes. But that isn’t the same thing. Why not? Because the ‘decision’ to flower, and usually the formation of embryonic flower buds, took place in the previous year, and they all sat dormant along a branch that grew in that same previous year (or maybe older) through winter, waiting for spring to return.

These buds can be of different kinds. Some plants have ‘mixed’ buds, that contain both leaves and flowers. Others have separate leaf buds and flower buds. Sometimes you can see see the difference in their shape – flower buds tend to be fatter, while leaf buds are more pointed. Other times you would need to dissect it under a microscope to know. But flowers are either there or not there – all through winter.

That’s why we say that plants like that flower on ‘old wood’. If you cut of the branches from the previous year, you won’t get flowers.

With many plants that bloom on new wood, you could prove this by cutting the tip off the branch once it has started to grow. Usually it will produce some side branches and still flower – you are doing what old-timers like me call ‘pinching out’. It’s a classic way of getting more flowers. Leave it too late, though, and you pass the point where tips make flowers, and you will end up with nothing. Do the same thing with a plant that blooms on old wood, and do it as early as you want, but if you cut the tip of the branches that come in spring, you will never see a flower. Try it with a mophead hydrangea, for example, where there is an early stage where you have a new leafy shoot, and no sign of a flower. Pinch out the tip and you get no flowers, period.

I hope that helps!

Usually, for all these reasons, plants that bloom on old wood are pruned after flowering, and those that bloom on new wood are pruned before flowering (normally spring).

October 28, 2023 by Liz

I have an old panicle hydrangea that reaches about 8′ and the base of its trunk is bigger than my ankle. It usually flowers well.
I’m not happy with its form. I usually cut it back in late winter by at least ⅓ or ½.
Does it make sense to cut it back to to 6″ from the ground?

October 28, 2023 by davethetreecenter

I don’t think such an old plant will regenerate successfully from a stump. Have you considered simply replacing it? These are fast-growing shrubs – it isn’t as if they take decades to mature, as trees and some shrubs do In 3 seasons you will have a good plant, and fully mature habits and form within 5 years. I suspect what you don’t like is its floppy habits, and many of the newer varieties have much stronger stems, like this one for example (although you might want something that will again reach 8 feet in flower). Ideally don’t plant the new one in exactly the same spot, but if you must, remove the stump and a couple of barrow loads of soil at least, and replace it with fresher soil from somewhere else in your garden – do a swap.

April 13, 2024 by Sally K

Well, I am still confused. How do we create a shape and balance while also leaving last years stems so that we have blooms this year?

It is April 13 here in Kentucky, zone 6. I already have lots of green leaves. My panicle hydrangeas need pruning and shaping. They are 5 years old.

I have current photos if there is a way to upload or email the photos. You could draw on them to demonstrate proper pruning, shaping, etc.

April 14, 2024 by davethetreecenter

First of all, we don’t run a free service like you are asking for. If your plants have leaves already, you need to prune right now, without delay. In future do it before the leaves appear.
Start off by removing all the thin, twiggy stems in the center, so you have an open form, with shoots coming off the top.
Now shorten those back to leave 3 or 4 pairs of buds/shoots only. I think once you have done that, it will automatically have the shape and balance you are looking for. From now on, prune annually, every spring – leaving them for 5 years makes it very difficult!!