Not all Rhododendrons are rhododendrons. Shrubs of the ancient genus Rhododendron are typically termed azaleas if deciduous and rhododendron if evergreen. Fossil evidence places them on earth over 50 million years ago with the same basic flower form and habit that they have today. Modern rhododendron species number in the thousands and range from tiny creepers to 35-foot trees. They thrive in U.S. Department of Agriculture plant hardiness zones 5 through 10. The shrub-size flowering rhododendrons considered garden staples require pruning for maintenance, shaping or rejuvenation.
Wipe the blades of your pruning shears with a rag dipped in denatured alcohol when the flower clusters, termed trusses, on your rhododendron bush begin to fade. Snip each truss off at its base, about one-half inch above new green growth.
Prune off dead and broken rhododendron branches. Make the cut at the base of the branch or at least 6 inches into healthy wood.
Inspect your plant for curled or wilted leaves. Prune back their branches to remove the diseased area, making the cut in healthy wood just above a dormant bud. Sterilize the blades between snips to prevent the spread of disease.
Shaping and Rejuvenation
Use your pruning shears to shape your rhododendron in late winter. Shaping will encourage thicker branching and can also control the size of the shrub.
Inspect the bush carefully before snipping. Note that each branch holds various whorls of leaves separated by a leafless section of stem. Determine which whorls you need to remove on each stem to enhance the shape of the shrub.
Shape the rhododendron stem by stem. Follow each stem down until all the whorls you wish to remove are above your hand and the whorls to remain are below. Make the cut one-fourth inch above the top leaf in the whorl of leaves just below your hand.
Prune the primary branches much deeper to rejuvenate a leggy or overgrown rhododendron. Identify latent buds on the stem, tiny pink dots that will grow into branches. Make each rejuvenation cut one-half inch above a cluster of latent buds. Cut as much as you need to, leaving at least a 24-inch stem to ensure the plant's survival.
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Things You Will Need
- Pruning shears
- Clean rag
- Denatured alcohol
- When pruning to rejuvenate a rhododendron, you create a more attractive shrub if you cut each primary branch at a different height.
- Although sometimes it is possible to prune rhododendrons back to within 6 inches of the ground, many shrubs are not able to recover.
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