The Complete Guide to Pruning Azaleas

Every proper Southern garden needs a beautiful bank of naturally shaped azaleas. Learn how and when to give yours a trim to make them look their best.

Photo: Van Chaplin

Each spring, azaleas light up our gardens with a profusion of colorful blooms. These classic mounding shrubs drift across the landscape like showy clouds. Once established, they need little care. Prune them correctly, and watch plants produce layers of beautiful bell-shaped flowers.

Which Type of Azaleas Need Pruning

Before you pick up any pruning shears, make sure you know what type of azalea you have. There are two classes of azaleas: native azaleas and Asian azaleas. Both are subclasses of the rhododendron family.

Native azaleas—sometimes called "wild honeysuckle" for their fragrant blooms with long stamens—are deciduous, meaning they lose their leaves in the fall. They never need pruning unless it's to remove a broken branch or diseased area of the plant.

Asian azaleas are the evergreen ones almost everyone in the South plants. Evergreen azaleas originally hail from Japan. Within this class, there are two popular groups: Kurume hybrids and Southern Indian hybrids.

Kurume hybrids, like 'Coral Bells,' 'Hino Crimson,' and 'Hershey's Red,' are dense, compact plants with small, glossy leaves and grow roughly 3 to 4 feet high. They bloom early and the flowers nearly hide the foliage.

Southern Indian hybrids grow at least twice as large and much faster than the Kurumes and aren't as dense. They also bloom about 1 to 2 weeks later and aren't quite as cold-hardy, so you see them mostly from the Carolinas south. 'George Taber' (pink), 'Formosa' (purple), and 'Mrs. G.G. Gerbing' (white) are popular varieties.

Why You Should Prune Azaleas

As with any plant, precision pruning can improve the air flow between branches and encourage new growth, making for a healthier plant. It can also keep some plant diseases—like powdery mildew—at bay. Selective snips can also help shape a plant into a pleasant, natural form that works well with its surroundings.

If you happen to have a plant that's overwhelming the space in which it's planted, you may have to take a more drastic approach to your pruning in order to get the azalea under control. You can cut overgrown plants down to about 1 foot in height without causing any long term damage to the azalea.

When to Prune Azaleas

Timing is critical if you want your azaleas to bloom next year. Since azaleas bloom on old wood, they produce flower buds on last year's growth. Ensure a riot of flowers to enjoy next summer and put up your clippers after springtime.

The best time to prune is within a three week period after they finish blooming in spring and have begun to discolor and shrivel. This gives the azaleas plenty of time to make flower buds (which appear as pale, fuzzy buds curled tight on the tips of branches) for next year. If you wait until the late summer or fall to prune, you risk cutting off the flower buds and all you will get next year is a bush full of green leaves.

Pink and White Azaleas in Garden
Alison Miksch

How to Prune Azaleas

Azaleas are beloved for their natural airy shape and look awful (and perform even worse) when sheared into boxy figures. Never use electric hedge trimmers when pruning azaleas; flat-topping your azaleas by trimming only the ends of branches will result in dense twiggy growth with sparse foliage. Instead, use mostly hand pruners to shape the bush into a soft, cloudlike shape.

Tools Needed

  • Small hand pruners or clippers for trimming pencil-width stems (smaller than ½ inch in diameter.
  • Long-handled loppers are the tool of choice when cutting branches ½ inch to 1 ½ inches in diameter. The handles provide the leverage needed to make clean cuts on woody limbs and allow you to reach into the center of shrubs.

Tip: Keep cutting tools sharp, so their blades make clean cuts when slicing through wood. Many quality clippers have replacement blades. Small files designed just for sharpening blades can also be purchased. Dull tools make pruning more difficult and will crush and tear stems.

Instructions

In most landscapes, azaleas look best when minimally pruned, allowing them to retain their naturally graceful form. Some azalea hybrids, such as Kurume, grow slower than Southern Indian hybrids and usually need pruning only once in 4-5 years. Southern Indians grow fast and may need trimming every year. Regardless of the hybrid, if it has been a while since your shrubs were shaped up, they have probably grown long woody stalks with clusters of foliage at the tips—a look that's often called "leggy". Here's how to clean them up:

Maintenance Pruning

Step 1: Remove long stray shoots by reaching down into the plant with your clippers and making cuts next to larger woody branches. The cuts will be hidden by surrounding foliage, but this thinning allows sunlight and air movement in the center of the shrub, which promotes healthy new growth.

Step 2: Cut back larger, thicker branches with loppers in the same manner, cutting to slightly different lengths to create a cloudlike, mounding shape.

Pruning to Control Size

Step 1: If you have a too-big azalea you want to save, go ahead and chop it down with loppers. Just don't take it all the way down; stop at about 1 foot off the ground.

Step 2: After pruning, feed the azalea with a slow-release, water-soluble fertilizer (12-6-6). Frequently water the plants you cut back to encourage a flush of suckers—sprouts of new growth—from the stumps.

Step 3: The following spring, the shrubs should be covered with lots of new growth. Reduce the number of shoots per stump to two or three, leaving only the strongest and best placed ones.

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