When to Trim Azaleas

How to trim your azaleas at the right time

Closeup of flowers of an orange azalea shrub.

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Project Overview
  • Total Time: 1 hr
  • Skill Level: Intermediate
  • Estimated Cost: $50

Azaleas are among the most popular spring-flowering shrubs and well worth the care they demand, including trimming. These Rhododendron genus members can be deciduous or evergreen. While trimming them has its benefits, it isn't always necessary. There are also steps to take that reduce the need for trimming. But learn when and how to trim azaleas in instances when it's necessary.

Reducing the Need for Trimming

Proper plant and site selection and the right care can minimize the amount of time you must spend trimming azaleas. Follow the maxim, "Right plant for the right place." Don't select an azalea with large mature dimensions for a spot that's up against a building or too close to another shrub. While azaleas generally like more shade than many flowering shrubs, they rarely do well in full shade. An azalea grown in full shade will become leggy because the shrub is reaching out to try to gain enough sunlight. It won't look very good, and you'll probably want to trim to reduce its legginess. Finally, if you want a compact azalea, don't feed it more than is required: This stimulates growth that you'll only have to trim off.

Before Getting Started

Decide whether bypass pruners or anvil pruners are the right tool for the job. Bypass pruners make a sharper, cleaner cut, which not only looks better but helps avoid pathogen infestations. Anvil pruners are also bulkier than bypass pruners, making it harder to make cuts in tight places. For these reasons, many gardeners prefer them for most of their pruning needs.

As a supplementary tool, have some loppers on hand. They have longer handles than pruners (giving you greater reach) and are designed to cut through branches of a greater diameter. These come in especially handy for trimming mature azaleas.

When to Trim Azaleas

Proper timing when trimming flowering shrubs is all about knowing when the shrub in question sets its flower buds for the next blooming season. Getting it wrong can mean removing the very buds you're relying on to give you the floral display you anticipate next year. It can be heartbreaking to learn that you've lost a year's worth of blooms because you pruned at the wrong time.

Prune azaleas immediately after they're done blooming. Because these bushes flower on old growth, pruning too late in the year deprives you of flowers for next year.

Is Trimming Azaleas Necessary?

The only trimming on azaleas that's truly necessary is to remove damaged, dead, crossing, and diseased branches, because leaving these can adversely affect plant health. Other than that, unless a mature plant simply isn't performing well anymore (in which case rejuvenation pruning is called for) or you have failed to follow the "Right plant for the right place" maxim, trim azaleas at your discretion.

What Is Rejuvenation Pruning?

Rejuvenation pruning is a drastic type done to revitalize a shrub that's overgrown and no longer performing well. The shrub is expending energy maintaining old branches that don't flower as they used to. Removing these old branches channels energy into the production of new, vital growth.

Conduct rejuvenation pruning in late winter. It entails cutting back one of the shrub's three or so main branches each year until all of them have been trimmed. Reduce the size of each main branch to about 1/3 of its old height, but make your cuts at slightly different heights for a more natural look. For each cut, go down to 1/2 to 3/4 inch above a healthy, outward-facing bud.

There are benefits to trimming azaleas, but many gardeners get years of enjoyment out of these shrubs with hardly any trimming. We all have our own unique tastes: One gardener's overgrown plant is another gardener's superstar specimen valued for its show-stopping size. The subjective nature of pruning is greater with some bushes than others due to what some people regard as their naturally delightful shape. As with Forsythia, some gardeners feel that trimming an Exbury-type azalea, for example, ruins the natural shape they find preferable.

Benefits of Trimming Azaleas

Assuming that you don't need to prune to correct a mistake (wrong location or improper care) or to rejuvenate, the main benefits of pruning are:

  • To open up the interior of the shrub, which improves air circulation and helps prevent fungal infestations
  • To improve the shape by removing stray shoots
  • To remove branches prone to catching (and spreading) disease, including branches that have open wounds due to mechanical damage

What You'll Need

Equipment / Tools

  • Bypass pruners
  • Loppers
  • Gardening gloves
  • Protective clothing

Materials

  • Isopropyl alcohol

Instructions

When your azalea is done blooming, this is the time to inspect it for dead, damaged, crossing, or diseased branches that need to come off, as well as branches that you simply feel detract from the overall shape of the plant. Here's what you need to do:

  1. Sterilize Your Tools

    When you trim a plant, you're opening a wound on it. To reduce the chance of infection, sterilize the pruners/loppers with isopropyl alcohol.

  2. Search for Unhealthy Branches

    Inspect the azalea for branches that are dead, damaged, diseased, or that cross over each other. Any of these could cause future disease and insect problems. Crossing branches rub against each other when it's windy and can open up wounds that become infected.

  3. Remove Unhealthy Branches

    Trim off the unhealthy branches you found. For crossing branches, select the most desirable one and trim off the other. This "maintenance pruning" is the most basic trimming you can do. Make your cuts close to the branch collar because you want to remove these limbs entirely.

  4. Prune to Shape

    If you find a gangling limb shooting out of the top of the plant, cut it down to 1/2 to 3/4 inch above a healthy, outward-facing bud. By selecting an outward-facing bud, you're promoting a limb that will radiate away from the center, keeping the center open. Leave it at whatever length you find most appealing, since the goal here is to foster a compact shape that's more attractive.