Pruning Panicled Hydrangeas And A Cure For Floppy Branches

Yes…the snowflakes are still here! Sighhhhhh

Hydrangea paniculata, often referred to as PeeGee(P.G.) Hydrangea, is a favorite shrub amongst home gardeners and professional landscapers. The name PeeGee or P.G. comes from the first cultivar commonly used- Hydrangea paniculata ‘Grandiflora’. Varieties like ‘Tardiva’, ‘Limelight’, ‘Little Lime’, and ‘Strawberry Sundae’ are some of the more well known varieties. For those of you who may be less familiar with this shrub it is the more woody hydrangea with lime-green and creamy-white panicle shaped flowers that, under the right weather conditions, often turns a rosy blush in the fall.



‘Little Lime’

Hydrangea paniculata is a godsend in the Midwest for hydrangea lovers due to its ability to withstand the intense humid heat of our summers without wilting everyday. They also will bloom on first year canes unlike many of the macrophylla, ball-head types which often will not bloom reliably for us central and northern gardeners. Hard winters don’t generally effect the blooms on Hydrangea paniculata. If you are a client of mine you probably have a couple of these hydrangeas on your property as I rely pretty heavily on their beauty, hardiness, and reliability in a border.

These may be woody shrubs or tree forms growing anywhere from 3 feet to upwards of 10 feet. They start blooming around mid-summer opening with a lime green panicle that tends to become more creamy as the summer goes on. Most of these turn a nice blush as fall approaches and many new cultivars are being produced like ‘Quickfire’ and ‘Firelight’that turn deeper rose or reddish hues earlier in the season.

‘Little Quickfire’

There is one issue that seems to arise with these seemingly perfect flowering shrubs. Sometimes they simply seem to grow to large! ‘Little Lamb’ being the first one that comes to mind. There is NOTHING little about it. The tag usually says it grows 4-6 feet tall and calls it a “compact” form when in reality it usually grows 6-8 feet tall. Gardeners then tend to try to prune these harder than the plant would like and it responds a in an ornery manner by growing back just as much as you pruned off, but now instead of the strong woody branches it developed while maturing over the years to support its large flowers, it has the more tender growth of the current season. These soft first year canes are unable to hold up the huge flowers and consequently flop in an rather unattractive manner.

Here is the rule: The harder you prune a Hydrangea paniculata the more new, soft growth you will get shooting out that year with a smaller number of blooms that are very large in size and very hard for the new shoots to hold up. The less you prune off of them the less new growth you will get that year with a greater number of blooms that are smaller in size and supported by an older, woody framework of branches. Personally I prefer a well supported bush with a lot of flowers even if they are a little smaller.

In order to have a nice looking shrub that can support its flower panicles without flopping you have two options. One is to make sure the shrub is in a location where it can be free to grow to the mature size it desires. This may mean that you must relocate your hydrangea if it is outgrowing its spot every year. You should give it a light, shaping prune each year where you take off between 6-12 inches on all sides and round it into a nice shaped framework. Late fall or early spring is the best time to do this.

Below is a picture of ‘Little Lime’ after I pruned 6-8 inches off of it just yesterday.

The other option for stubborn gardeners, such as myself who insist on having these hydrangeas in a location that is too small for their natural size, is to use a trick to keep them under control. But just a fair warning- this requires a bit of tough love! The ‘Little Lime’ hydrangea in the picture above is in fact in a very tight spot and I must keep it on a very tight leash.

So… the trick is to prune twice in one season, once early and once later in the spring. Yes…I did just say that. Pruning in late spring has always been a huge no-no when it comes to hydrangeas, but not in this case. You prune them hard in late fall or early spring taking off 12-24 inches. You want to prune to about 6 inches below what you consider the ideal size to be when it is blooming. Here are the before and after pictures of the one on the front of my house with a hard pruning I did today.

You allow the hydrangea to flush out for the spring until about June here in the Midwest, and then prune it again. I generally take 6-8inches of new growth off at this time. In the picture below the ‘Little Lime’ Hydrangea is on the right side of the photo and shows how it should look when it is ready to receive this second pruning.

Your shrub may look a little sad for about 2 weeks and then it will recover and flush again but not as much as it did in the spring. It will develop flower buds and bloom just fine, though the flowering will be delayed by 2-3 weeks.

Just in case you can’t quite bring yourself to believe me I did an experiment where I pruned the upper part of one of my bushes twice as mentioned, and the lower part just the one time in early spring. I then took a picture of that shrub in the fall. You can see below what the results were. I actually pruned the top after there were already some small flower buds present, so quite late(too late really) in June, and it still flowered! This picture was taken towards the end of September so I had fresh new flowers coming on in the fall. Ideally I would not want my blooming delayed quite this much so I don’t recommend doing the second pruning any later then the first week of June.

This discovery actually came about as a result of deer grazing on one of my client’s gardens. The deer-grazed hydrangeas actually came back looking better than ever, though now they were covered in bird netting to break the eating habits the deer had developed. It is probably one of the only instances where deer damage let to a positive outcome.
There are quite a few perennials that also respond well to a late spring pruning to keep them a little bushier and less likely to flop over. Phlox, Agastache, and Sedum are a few examples. You may have noticed that occasionally when a sedum like ‘Autumn Joy’ gets munched on by rabbits it actually ends up being shorter, bushier, and holds itself up better, so long as the damage is not severe and continuous. I love lessons nature sometimes reveals to us- don’t be afraid to experiment a little!

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