Do you need help knowing how to prune a Hydrangea paniculata?
Hydrangea paniculata is an extremely common landscape plant, and for good reason. It has beautiful summer blooms that remain on the plant all winter giving it an extended season of interest. It is also sun loving, cold hardy and extremely easy to grow.
As you might also now know, it is not only beautiful. It is capable of growing to massive dimensions if left to its own devices. It is not uncommon to see old Hydrangea paniculatas that are as large as a small tree. While these plants are spectacular to see, realistically most people do not have a 20’ space in their back yard garden to devote to 1 plant.
Fortunately, if you start pruning them while they are young, they are fairly easy to keep to manageable dimensions. Even if you have a massively overgrown Hydrangea paniculata, it can easily be pruned back to a more manageable size.
Hydrangeas respond very well to pruning, and winter is the best time to prune your hydrangea. So grab your pruning shears, and join us in the garden.
Don’t be afraid to prune your overgrown plant ruthlessly. If it is a healthy plant, it is very unlikely you will harm it. Also, don’t be too worried about screwing up. Hydrangeas are extremely forgiving. If you don’t like how it turned out this year, consider it a learning experience and try again next winter.
Please Note:
There are several different kinds of hydrangeas, and they are not all pruned the same way.
If you do not know which type of hydrangea you have, it is very easy to tell the 4 commonly planted kinds apart. The two most commonly planted hydrangeas are mophead hydrangea (H. macrophylla) and panicle hydrangea (H. paniculata). Most likely you have one of these two.
Mopheads, are the ones that typically come in shades of pink and blue, and produce an orb of clustered flowers. They are the color changing hydrangeas like ‘Endless Summer’. These plants grow long generally un-branched, semi-woody stems from a cluster at the ground. Each year new shoots come from the ground.
Panicle hydrangea, the one we are pruning in this article, are a very woody plant. They usually have white more pyramidal shaped flowers. The plant grows from a single trunk coming out of the ground that is highly branched. Panicle hydrangeas include varieties like ‘Limelight’ and ‘Quick Fire®”.
The 2 least common types are always planted in shady locations. Oakleaf hydrangeas (H. quercifolia) have leaves shaped like large oak leaves. Snowball hydrangeas (H. arborescens), like ‘Annabelle’ or ‘Incrediball®’, have semi-woody stems and big round puffy, typically white flowers.
The basics
If you are new to pruning, you should know, that when you cut a branch off a plant, you always want to trim it back to a place just above a bud. This allows the plant to quickly heal over the injury you created by pruning.
Buds are easy to find on most plants. In the case of H. paniculata the branches usually have 2 or 3 buds opposite each other about every 6”. Unless you wish to increase the size of your plant, we will be pruning every single branch back to 1 bud above last year’s growth as shown in the above picture.
If you are dealing with very old wood, buds may be difficult or impossible to find. In that case just do your best. Next year you can clean up your cuts and will be able to clearly see the buds on the new growth for pruning.
No hedge shears please!
It is also always best to hand prune deciduous shrubs rather than shearing them with hedge trimmers. Why? They are not a hedge. Hedge trimmers cause the outer shell of leaves to get thicker and thicker every year. While this works with your hedges, on a hydrangea this tends to leave you with ugly plants that have bare spots on them. Additionally, they are often more prone to disease and pest problems too.
Deciduous plants grow vigorously, and benefit from being thinned yearly. By properly hand trimming them you will ensure that your plant stays healthy, and looking nice. It will also ensure that you get those big beautiful blooms you are looking for.
If you have a shrub that has been sheared
If you have a shrub that has been sheared for several years, the first thing that you want to do is trim off that outer shell of matted branches. You must undo the damage that years of shearing has done to your plant. The goal is to get rid of all the weak branches and those growing the wrong directions. After you have done that, go through and thin other branches as needed to create a uniform shaped plant that is open enough to allow air flow.
Remember every time you cut a branch, it is going to produce 2-3 more branches from the buds nearest to where you cut it. Thin the plant enough that there is space for each of these new branches to grow. For example, in the above picture, the best course of action would be to cut this messy branch back to a stub that has no side shoots. This plant has no shortage of branches, and removing the messy knot now will allow us to have nice easy pruning in future years.
After this first year, where you must undo the damage done by shearing, pruning will be easier.
In subsequent years, find the place where you pruned the shrub to last year. Prune each branch off above the 1st bud. (refer back to Figure 2 if necessary). This might mean that you are removing several feet of stem. This is ok. That 4’ of stem grew this year. If you don’t remove it the plant will put on another 4’ of growth on top of that next year. Trimming the plant back significantly in the winter keep it sturdy, and helps keep it to a similar size year to year.
Now, if you just prune off to the first bud on every branch every year, you are essentially doing the same thing that hedge shears are doing. So as you are pruning back, you also need to be thinning your shrub.
How do we do this?
Easily. Similarly to how we first trimmed off the branch ‘shell’ that hedge shears made. Every year remove some of the branch knots you have created by pruning. You do not have to remove every single one every year. Just remove the most gnarly 25% or so. This will allow you to keep the shrub open. Also by limiting the number of branches, you are ensuring that you will maximize the size of your blooms.
Plant still to big?
If the shrub out grows its space despite your winter pruning, you can prune it again after it has put out its initial flush of growth in the spring. If you prune off half of the new growth, and allow the plant to flush again it will be smaller for the remaining portion of the season. The plant has put most of its energy into the spring growth, so growth after summer pruning will be less vigorous.
If you prune your hydrangeas back before they bloom, keep in mind that this will delay flowering. An alternative option is to wait until after they have flowered and then trim them back. In areas with longer growing seasons, the plants will often stay smaller and re-bloom if trimmed after flowering.
On a plant that you have hand pruned and thinned in the winter, summer pruning is quick and easy. This is because you have a relatively small number of large, straight stems that can quickly be cut in half. You can see an example of how few stems you would need to prune, and how easy it would be to summer prune the un-pruned plant in the first picture (Figure 1).
What if I have a massively overgrown shrub?
If you have a badly overgrown shrub, you may need to get out loppers or even a pruning saw. You will need to trim the shrub back to a size which you deem to be appropriate. Keep in mind that it will grow back vigorously after pruning, so trim it smaller than you want its mature size to be.
Simply cut back the branches to stubs of your desired height. This is very similar to/essentially the same as the pruning technique called ‘rejuvenation pruning’. When done with this your shrub might consist of something like 6 stubs that are 3’ tall.
At this point, you might be panicking at just the thought of doing this.
Rest assured, you are not alone. The thought of pruning a shrub so harshly is paralyzing to many gardeners. However, hydrangeas and many other deciduous shrubs actually benefit from this type of pruning. They typically grow back better than ever if rejuvenated occasionally.
In the spring your stubs will flush out with tons of new branches from dormant buds.
That first summer you most likely will not need to do anything to the plant except enjoy it. Come winter though, you will likely need to do some thinning.
To thin your ‘new’ shrub, you will follow a similar method as we first discussed. Only this time you will not have knots of old growth yet.
Go through and remove all the excess branches. Start by removing the thin, weak ones, and the ones growing at odd angles or in terrible directions. If you have stubs that didn’t grow, or that grew branches from the base instead of the top, remove the excess stub. Then thin the remaining branches to be evenly spaced. Select sturdy, well attached branches that will create a solid structure for your new shrub. Try to create something that will look similar to the above picture in a few years.
After the first year’s severe cutback and thinning, you can resume pruning your shrub using the techniques we discussed above for pruning non-overgrown shrubs. Harsh rejuvenation type pruning is not something that should be performed frequently, but it can be done periodically if needed.
We hope this gives you the courage you need to tackle pruning that overgrown hydrangea threatening to eat your garage!
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