Tough old rhododendrons can present a challenge for gardeners, mostly because of the hardened cells in the vascular bundles that become plugged and lose their ability to function normally. To revitalise your rhododendrons, you must adopt some extreme pruning measures to uncover new wood. Drastic pruning of your rhododendron should only be performed in the spring or early summer for best results.
- Skill level:
- Moderately Easy
Things you need
- Pruning shears
- Gardening or work gloves
Cut the plant down until it is just several inches above the ground for best results on multiple-stemmed rhododendrons. This does not always lend a pleasant appearance to your landscaping, and caution should be used as this can kill hybrid rhododendrons that only have one stem.
Reach down into the shrub with pruning shears and remove one-third of the old wood if you want to opt for a less drastic pruning method. This must be done over the course of three years, but it allows enough leafing surface to supply nutritional support for the return of new growth in the plant.
Remove storm-damaged areas of the rhododendron from the plant as soon as possible.
Check for stems exhibiting disease, such as wilting or yellowed leaves. Cut damaged or diseased limbs below the area of distress in a healthy piece of the branch just above a dormant bud.
Perform maintenance pruning after flowers have faded and before the swell of new growth beneath the trusses reaches more than an inch or so. Not all rhododendrons require maintenance pruning, but the ones that do fare best when pruning is done then.
Add shape to your rhododendrons by snipping just above the leaves you plan to keep.
Remove old trusses from faded flowers by snipping with a pruning sheer at the base of the truss. Cut half an inch above the new growth on the plant to avoid bruising it.
Tips and warnings
- If you cut diseased areas, disinfect your shears with rubbing alcohol before trimming other parts of the plant.
- Most broad-leaf evergreen rhododendrons and deciduous azaleas benefit from maintenance pruning. Those that rarely set seed will not require such pruning.
- Flowers and stalks that shrivel on their own and vanish do not need to be deadheaded.
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