Knowing when to prune shrubs can be complicated with all the conflicting advice out there. Here’s a simple explanation to help clear things up.
So many different shrubs and all of them are different.
Some are deciduous and some are evergreen. Some flower, some don’t. The ones that do flower, flower at different times. If that’s not confusing enough some flower on old wood and some on new wood.
It can be overwhelming to figure out when to prune shrubs in your landscape when they all have such different characteristics.
Luckily, it doesn’t have to be complicated. Stick to these simple rules and make things easy on yourself.
Prune Shrubs After flowering
Lots of people with flowering shrubs are afraid that pruning at the wrong time will cut off the flower buds, which will ultimately lead to a shrub that barely blooms.
This gets confusing because some shrubs get their flower buds on the current seasons growth (new wood) while others get it on past seasons growth (old wood).
People think they have to research each shrub to determine if they have a shrub that flowers on new wood or old wood. For the everyday homeowner this can be frustrating and an annoying waste of time.
Luckily, it isn’t necessary to make things so complicated.
Doesn’t matter if your shrub flowers on old wood or new wood. There’s no risk of cutting off next seasons flower buds because they haven’t developed yet.
When pruning right after the flower bloom period it is important to realize that plants are still actively growing. At this point you only want to take off the top growth and shape the plant.
When plants are actively growing you don’t want to do a severe pruning where you cut the plant way back. Severe pruning is best done when the plant is dormant in early spring.
Early Spring for Severe Pruning
If you have shrubs that are very misshaped, overgrown, or developing a bad branching habit they may be in need of a severe pruning.
A severe pruning is where you are cutting way into the shrub. This means you are cutting branches that developed multiple seasons ago.
This kind of pruning is best done in very early spring while the shrub is still dormant. This causes less stress to the plant and also encourages new growth.
For shrubs that flower on old wood such as forsythias, lilacs, and rhododendrons you have to prepare yourself that if you do a severe pruning in early spring you will not get a lot of blooms on these plants for the upcoming season.
Cutting off flower buds is a sacrifice you sometimes have to make. This type of pruning is not something that has to be done every season. It is mostly for shrubs that need to be trained into a better growing habit or for shrubs that are overgrown.
At some point during the summer almost all shrubs need a light pruning. Summer pruning is meant to shape the plant.
You are not cutting off wood deep in the plant, instead you are cutting off soft, green branches from the current growing season.
A light pruning will create a cleaner looking shrub and also encourage a thicker branching habit.
Avoid Fall Pruning
Contrary to a lot of information out there, fall is not a good time to heavily prune shrubs. There are 3 main reasons why fall is a bad time to prune:
1. Pruning Encourages Growth. This is great in spring, but come fall plants are starting to store energy and get ready to go into a period of dormancy. This is not a time where you want energy being spent on new growth.
2. Increase Risk of Frost Damage. When you prune, an open wound is created on the ends of the pruned branches. These are vulnerable places that can easily be damaged by frost. This will leave you with long sections of dead branches in spring.
3. Risk of Cutting Flower Buds. As discussed earlier, any shrubs that flower on old wood already have next seasons flower buds on them in the fall. If you prune heavily into the shrub at this time you won’t have as many blooms next season.
Light Prune As Needed
At any point during the season shrubs might require a little touch up pruning.
Maybe it’s early spring and you see some dead branches or dead tips of branches that formed during the winter.
Maybe its late summer and you notice that after your summer pruning there are some random shoots of new growth.
Whatever the reason, you are safe to do a light pruning at any time.
When to Prune Hydrangeas
Just about half the pruning questions on the internet are related to pruning hydrangeas.
Hydrangeas are one of the best shrubs for long lasting flower blooms and can add a lot of color, especially to shade gardens.
People take their hydrangea blooms seriously. They look forward to them all year and it is one of the most likely flowers people will cut and bring into their home to enjoy.
It can be very disheartening if your hydrangeas fail to bloom, and the likely cause is incorrect pruning.
If you want a detailed education on the different kinds of hydrangeas and how they should be pruned, check out this write up.
If you’re looking to keep things easy, pruning hydrangeas is very similar to the rules outlined above:
1. For hydrangeas that bloom on new wood cut the shrub way back to the ground in very early spring. Remember, this is the best time of year for severe pruning.
2. For hydrangeas that bloom on old wood stick to the prune after flowering rule.
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