In the past, I would get paralyzed, wondering whether I was pruning our shrubs at the right time. Now that I understand the basic pruning principles, I thought I would share them with you. Love it or hate it, most shrubs benefit from light to moderate pruning each year. Let’s look at how to take the mystery out of pruning shrubs.
I remember the first time I heard the terms old wood and new wood when I asked about pruning hydrangeas. This was so strange to me. How am I supposed to know what old wood vs new wood looks like? So, while talking about old and new wood regarding pruning is technically correct, I think it’s better to simIply talk about what to prune and when.
In this article, I will discuss basic pruning guidelines for shrubs. In addition, we will take a tour around our property and discuss when to prune various spring and summer blooming shrubs.
Estimated reading time: 12 minutes
Why prune?
First, a definition. Pruning is simply the removal of unwanted portions of a shrub. Think of a pruning cut as a wound that needs to heal. Therefore, always try to do small, smooth cuts. Doing mindful cuts and pruning at the right time of year will ensure that the wound heals properly. Understanding why to prune is the first step in how to take the mystery out of pruning shrubs.
Here are some reasons why you might consider pruning your shrubs:
- To maintain plant health. Just recently, I was pruning dead branches from one of our rhododendrons. Because these dead branches could harbor insects, it’s good to prune them out. In addition, when a shrub is overly dense, then pruning will promote air circulation and reduce the potential for disease.
- For appearance. We prune our forsythia to maintain a hedge appearance. Pruning our Little Lime Hydrangeas maintains their overall shape.
- To restrict growth. Each spring after our azaleas flower, we prune the dead flowers and new growth to maintain the overall size of each plant. The same is true for our Amsonia blue star plants. After blooming, Amsonia puts on vigorous growth. To maintain their size and not block out other plants we prune.
Pruning tools
A few considerations to keep in mind when it comes to tools. First, maintain sharp tools. This will ensure a smooth pruning cut and thus allow the plant to heal quickly. Second, disinfect your tools after every use with a wipe of rubbing alcohol. This will prevent disease spreading from one plant to another. Using the right tools is the second step in understanding how to take the mystery out of pruning shrubs.
Bypass Hand pruner is used for cutting branches up to 1 inch in diameter. In addition, bypass pruners, as shown below, reduce tearing when making a cut on branches. Bypass pruners have two curved blades that slide past each other like scissors. This is my favorite pruning tool. More specifically, I like the Fedco brand.
Pruning Shears, sometimes called hedge clippers, are used for hedges. These are large shears with a long handle.
Hedge cutters deal with more heavy-duty work. For example, due to the length of our forsythia hedge, we use an electric hedge cutter. Pruning shears would require too much manual labor.
Lopping shears or loppers. With their long handles, use loppers for cutting branches 1.5 to 3 inches in diameter. Think of these as an amped-up version of hand pruners. We tend to use loppers mostly on tree branches but occasionally on shrubs.
When to prune?
The time to prune is based on the shrub’s flowering or growth characteristics. Late summer and early fall are not good times to prune any shrub (August through October). Pruning during this time does not give the plant time to heal before winter.
While appropriate to discuss timing based on whether shrubs bloom on old or new wood, there are other ways to know when to prune. Here are some easy guidelines to remember. I have come to follow these guidelines and they have worked quite well. Timing is the third step in understanding how to take the mystery out of pruning shrubs.
- Spring flowering shrubs should be pruned right after flowering and before the end of June. Most bloom on wood stems from the prior year (old wood) and the buds are set on their stems after June. If you prune later than June, your risk cutting off the buds that are your flowers for next season. Spring blooming shrubs include azalea, rhododendrons, viburnum, lilac, forsythia, honeysuckle, and weigela. The best rule of thumb is to simply prune after the plant finishes blooming.
- Summer and autumn flowering shrubs should be pruned in late winter or early spring before new growth appears. These shrubs set their buds on new wood growth that appears in spring. Shrubs in this category include beautyberry (callicarpa), abelia, summersweet (clethra), panicle hydrangea, Bluebeards (caryopteris), and butterfly bush.
- Prune shrubs without flowers when they are dormant in late winter or early spring. This includes most needled evergreens and many “non-flowering” broadleaved evergreens such as holly. Also included are shrubs such as red twig dogwood, boxwood (Buxus), and burning bush (euonymus alatus).
Special pruning situations – Hydrangea
Now, let’s talk more specifically about hydrangeas. We have five different varieties of hydrangeas growing on our property and we treat them differently.
- The first hydrangeas we planted were the hydrangea bigleaf or hydrangea macrophylla. I can remember how frustrating it was when these did not bloom. I have come to realize that I had two problems. First, we pruned at the wrong time. These hydrangeas bloom on old wood and so basically you should leave them alone. Maybe, prune out dead branches in the spring as growth is beginning. The second is deer. Bigleaf hydrangeas seem to be a favorite of the deer population on our property. This is a problem that is more difficult to solve especially if the deer have chewed down the branches with buds.
- The next type of hydrangea we planted was oakleaf hydrangeas or hydrangea quercifolia. For some reason, I thought these bloomed on new wood. However, that is not the case. These also bloom on old wood and so again leave these alone when it comes to pruning. Prune only for the reasons mentioned earlier, health, appearance or to restrict growth. These hydrangeas can grow up to 15 feet tall and have huge blooms.
- Last, we purchased 3 varieties of panicle hydrangeas: Little Lime, Little Quick Fire, and Fire Light. Since these hydrangeas bloom on new wood, prune in the spring before or as new growth is beginning. While the deer still like these hydrangeas, the panicle hydrangea recovers more quickly. We really love the panicle hydrangea and recommend them as a more carefree hydrangea.
Special pruning situations – Spirea
Spirea is another shrub that I consider a special consideration. This shrub blooms on new wood and so the best time to prune is early spring. However, we have found that spirea benefits from pruning multiple times. I prune dead flowers over the summer and am always rewarded with new blooms.
A tour of shrubs on our property and pruning thoughts
Spring blooming shrubs
Korean Lilac (Syringa ‘Palibin’) – This lilac blooms in early spring on old wood. Therefore, pruning should occur shortly after blooming to avoid cutting off buds for the following year.
Azalea is in the foreground and Holly is in the background. Azalea blooms on old wood and therefore should be pruned just after blooming. We prune our azalea for shape. Holly is an evergreen and we prune both to control size and shape. Pruning Holly has also encouraged the plant to fill in bare spots.
Forsythia hedge along our driveway and into the backyard. Forsythia blooms in spring on old wood and therefore should be pruned immediately after blooming. However, we prune our forsythia hedge 2-3 times a year depending upon growth. The second and third times are to remove the top growing stems to keep the hedge looking uniform.
Summer blooming shrubs
Leucothoe is an evergreen plant that does not require regular pruning. This is one of the most carefree shrubs in our landscape.
I really love our Bluebeard (caryopteris) plants. They tend to be inconspicuous but are rather beautiful up close. To be honest, we have never pruned our Bluebeard and they faithfully come back every summer. Bluebeard bloom on new wood and therefore benefit from late winter or early spring pruning.
Calliparpa blooms in the summer on new wood. In early spring, we prune this shrub back to about 12 inches from the ground. This is another beautiful shrub with both summer and fall interest. Flowers in the summer and berries in the fall.
A summer blooming shrub, abelia blooms on new wood. We prune our abelia shrubs in early spring just as new growth appears.
Here we have a trio of plants. In the far background is the Hydrangea paniculata grandiflora ‘Little Lime’. This variety blooms on new wood in early summer. It can be pruned back in late winter or early spring. Next comes Clethra ainifolia. Clethra blooms on new wood in early summer. We cut back dead twig ends in early spring. In the forefront is viburnum carlesii which blooms on old wood. Therefore, we prune in the spring right after flowering.
Additional Information
You may find the following articles interesting.
- The garden shed as a focal point in your landscape
- Brilliant method to create new garden beds – lasagna gardening
- Prepping garden beds for the season
- 5 pieces of planning advice for the vegetable gardener
- 6 easy steps to divide Siberian Iris
- Nine wonderful perennial flowers that animals will not devour
References
University of Minnesota Extension
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