How and When to Prune Rhododendrons

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A gardener's guide to shaping a rhododendron and keeping it healthy
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With their lush greenery and beautiful flowers, rhododendrons (and azaleas, which are included in the Rhododendron family) make a beautiful addition to any landscape. Pruning a rhododendron properly will help maintain its shape and can even encourage more blooms in future years. We’re sharing three different ways to prune your rhododendron, plus tips on when and how often to prune and where to make your cuts.

When to Prune Rhododendrons

After your rhododendron finishes blooming in the spring, remove spent blooms and dead branches to encourage flowering next year. If your rhododendron is overgrown, shape it in either mid to late winter or early summer. To drastically prune a leggy rhododendron—known as radical rejuvenation—cut it back in late winter.

Section 1 of 6:

Annual Maintenance Pruning

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  1. 1
    Remove spent blooms and dead limbs yearly. Do maintenance pruning about once a year on most rhododendrons to get the most flowers the following year. If your rhododendron produces seed pods, prune away the flower clusters every year after blooming is finished. This is also a good time to inspect the plant for broken or diseased branches. [1]
    • If your rhododendron doesn’t develop seed pods (the flowers just shrivel up and disappear when blooming is finished) and it doesn’t drop many leaves each year, it may not need annual pruning—just shape it every few years as needed. [2]
    • Many azaleas don’t produce seed pods and don’t need to be pruned annually, either. [3]
  2. 2
    Do maintenance pruning in late spring. Wait until your rhododendron has finished blooming to do maintenance pruning so you can fully enjoy the flowers. This will typically be in spring, but the exact timing could vary depending on where you live.
    • Avoid maintenance pruning in the summer after around July. This is when your rhododendron starts to set its buds for next year, so if you prune after this point, you won’t have blooms the next year. [4]
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  3. 3
    Start by removing the spent blooms. Use pruning shears to snip off the spent bloom clusters. Look for new green growth on the stem just under the spent blooms—make your cut about 1 ⁄ 2  in (1.3 cm) above that, being careful not to damage the new growth. [5]
    • This process is called “deadheading.” It prevents the flowers from turning into seed pods, so the plant can put more energy into new growth and next year’s flowers.
    • If you want, you can use your fingers to pinch off the spent blooms, but it will be harder to avoid damaging the new growth.
  4. 4
    Cut back dead or damaged branches. Every year after deadheading, examine your rhododendron, looking for branches that are dead, broken, or turning a different color than the rest of the plant (which can indicate disease). Use pruners or loppers to cut back damaged branches. [6]
    • Either cut off just the damaged portion, making your cut just above a leaf whorl, or cut the entire branch back to the base so your cut is flush with the main stem.
    • If you’d like your rhododendron to be bushier, you can also pinch back new growth at this time. Look for areas where one single shoot of new green growth is emerging from the end of a branch. Use your fingers to pinch off this shoot—more than one shoot should replace it in just a few weeks. [7]
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Section 2 of 6:

Shaping an Overgrown Rhododendron

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  1. 1
    Shaping rhododendrons as needed every few years. Shape your rhododendron when it starts getting a little overgrown, losing its shape, or getting so tall that the inner branches can’t get light. You’ll usually only need to do this every few years. [8]
    • If you have a fast-growing rhododendron or you prefer it to have a more compact shape, you might shape it every 2–3 years. If your rhododendron is slow-growing or you prefer a more natural shape, you might lightly shape it every 3–4 years at the most.
    • If your shrub is near a walkway, you might only need to prune it when the branches start growing into your walking path.
  2. You have two options for when to do a shaping prune on your rhododendron: In the mid to late winter when the plant is dormant (as long as you don’t prune during a freeze), or in the early summer, before July. There are pros and cons to each:
    • Mid- to late winter: If you shape your rhododendron in winter, you may have less of a chance of damage due to pests or disease. New plant buds will start to form as the plant comes out of dormancy, which can create a denser, bushier shrub. However, your rhododendron probably won’t bloom in the following spring because you’ll be removing the set flower buds. [9]
    • Early summer: If you prune in early summer after your rhododendron blooms, the foliage will be at its fullest. This may make it easier to see where to make natural-looking cuts, and you’ll probably still get flowers the next year. [10] However, any new growth may not have time to fully harden before winter, so your plant may not be as full for the next year.
  3. 3
    Trim overgrown, crossed, or damaged branches. Prune any branches that are growing out past the shape that you want your rhododendron to have. Also cut back tall, straight branches that might be blocking sunlight and air from reaching the center of the plant. And any time you’re pruning your rhododendron, check for any damaged or diseased branches. [11]
    • When you’re pruning a shrub, look for branches that are crossing or tangled—these will compete for space, and you’ll make the shrub stronger by removing one or both.
    • Use pruning shears if a branch is less than 3 ⁄ 4  in (1.9 cm) in diameter. If it’s bigger than that, use loppers .
  4. 4
    Cut above a whorl of leaves if you’re leaving some of the branch. If you want to leave part of your branch—like if it’s only a little taller than the branches near it—look for a whorl (or cluster) of leaves near the height you want the branch to be. Make your cut just above the leaves so you won’t have a stubby, bare branch sticking out of your shrub. [12]
    • Leaving part of a branch is known as a “heading cut.” You’ll often see two branches emerging from this cut once new growth starts to appear, so these cuts are sometimes used to encourage a bushier plant. [13]
  5. 5
    Cut the branch off flush if you’re removing the whole thing. If you prefer to remove the whole branch, cut it all the way back to where it emerges from its parent stem. This can be a good option if a branch is broken or diseased, or if it’s grown leggy (meaning leaves only appear at the very end of the branch).
    • Cutting the branch all the way back is known as a “thinning cut.” These are more common than heading cuts—they help improve airflow and sunlight to the remaining branches, making the overall plant stronger.
  6. Rhododendrons tend to look best if they have a somewhat wild, natural shape. Don’t cut the branches all the same length, and try to maintain the overall shape as you trim. [14]
    • When you’re choosing where to make your cuts, try to mimic the natural growth pattern of your rhododendron—the branches will be different lengths, and while the shrub might have a generally round or oval shape, it won’t be perfectly defined.
  7. 7
    Avoid cutting more than 1/3 of the branches at a time. If you cut too much of your plant at one time, you could stress the plant, which can make it susceptible to disease or even kill it. If your rhododendron needs more dramatic shaping than you can do in a year, allow it to recover, then shape it again the following year. [15]
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Section 3 of 6:

Radical Renovation for Leggy Rhododendrons

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  1. 1
    Use radical rejuvenation only for leggy, overgrown rhododendrons. Radical rejuvenation can help restore rhododendrons that are extremely overgrown. This might be a good option if your shrub has become lanky and leggy, meaning you only see leaves and flowers forming on the ends of long stems. [16] You might also choose radical renovation if your rhododendron doesn’t flower anymore. [17]
    • Radical rejuvenation is a severe pruning method, and not all rhododendrons will recover. If your rhododendron is healthy and there are leaves on the full length of most of the stems, try regular shaping first—even shaping over a period of several years, if you need to. [18]
  2. 2
    Perform radical rejuvenation in winter. Winter pruning is better for more shocking trims because the plant is dormant, so its energy is not in its leaves or flowers. Cutting in the winter is the best way to ensure that your plant will have new growth after you prune it. [19]
    • If you cut in winter, you probably won’t get flowers the following spring (or for several years, in some cases), but your rhododendron will have the best chance of recovering. [20]
    • Don’t prune during a freeze, as you could damage your shrub. [21]
  3. 3
    Cut no more than 1/3 of the rhododendron’s branches. Although some rhododendrons can survive being cut back all at once, others can’t. The safest way to drastically cut back your plant is to cut back about 1/3 of the branches once a year for 3 years. After the third year, you will have pruned the entire plant. [22]
    • The only way to know whether your rhododendron can survive a more drastic pruning is to cut it back and see if it recovers. But since there’s a pretty strong risk that your rhododendron won’t come back, only do that if you don’t mind losing it. [23]
    • You could also cut one of the main stems back and watch to see whether it recovers the following year. If it does, you could cut the remaining two stems back to the ground.
  4. Most rhododendrons have three main branches coming out of the base, or crown, of the plant, with smaller branches growing from these. If your plant needs a radical rejuvenation, choose one of these primary branches and cut it back so it’s about 1–2 ft (0.30–0.61 m) long. [24]
    • Since you’ll be cutting the rhododendron’s thick, primary branches, use a pair of loppers to make the cuts.
    • When you’re choosing where to make the cut, examine the branch. Look for a cluster of tiny pink dots—these are latent buds, and they’ll form new shoots in the following years. [25]
  5. 5
    Repeat by pruning another main branch each year. Give your rhododendron a year to recover from this drastic pruning, then cut back another branch the following year. Keep going one year at a time until you’ve pruned the whole plant. [26]
    • Stagger the length of the primary branches so they’re all slightly different lengths—this will give your rhododendron a more natural shape.
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Section 4 of 6:

Pruning Best Practices

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  1. 1
    Fertilize your rhododendron about a month before you prune. A little planning ahead can give your rhododendron extra nutrition to recover from pruning. Applying a fertilizer for azaleas and rhododendrons to the soil about a month before you plant to prune will help the shrub develop more dormant buds—and therefore more new growth. [27]
    • Carefully follow the label instructions on the fertilizer—rhododendrons and azaleas don’t need much fertilizer, and they can be damaged if you use too much.
  2. Always sanitize your pruning tools before you start cutting to prevent spreading bacterial or fungal diseases from one plant to another. The easiest way to sanitize them is to wipe them down with 70% rubbing alcohol. [28]
    • Also, be sure your pruning tools are sharp—either sharpen or replace them if they start to get dull. Dull tools can tear the bark, leaving your rhododendron susceptible to insects or disease. [29]
    • Use pruning shears if you’re cutting branches that are 3 ⁄ 4  in (1.9 cm) or less in diameter. For branches that are up to 1 1 ⁄ 2  in (3.8 cm) in diameter, use lopping shears . You’ll rarely see rhododendron branches that are larger than that, but if you do, use a hand saw . [30]
  3. Try to avoid bending or breaking the branches of your rhododendron. Instead, use your tool to cut the branches evenly and in straight lines. This will cause less damage to your plant, and will lessen the chances of it going into shock or dying. You can make your cuts on any part of the branch—new growth will emerge from tiny latent buds under the bark. [31]
    • Place a tarp beneath the area you are cutting for an easier cleanup of branches and leaves.
  4. 4
    Embrace the rhododendron’s natural form. Rhododendrons look their best if they’re allowed to keep a natural shape, with branches of varying lengths. Also, some varieties of rhododendrons can grow very large. If you find yourself having to constantly prune the plant because it keeps outgrowing its space, consider replacing it with a smaller variety or a different plant. [32]
  5. 5
    Keep the rhododendron’s soil lightly moist over the coming year. Pruning can be hard on a plant. To keep your rhododendron healthy and growing, be sure it doesn’t dry out too much throughout the next growing season. [33]
    • You may also want to add fertilizer again in the coming months—but because rhododendrons don’t usually need a lot of fertilizer, it’s a good idea to have your soil tested by your local agricultural extension office to see if you need to add anything.
  6. Some rhododendrons become overloaded with flowers when they bloom. Blooming requires a lot of energy, so this can deplete the plant. To improve the overall health of your shrub and get showier flowers, pinch off a few of the flower buds each year before the flowers start opening. [34]
    • It’s up to you how many to remove—if you see a cluster of 7 flowers forming, you might pinch off 3 or 4 to create a smaller cluster, for instance.
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Section 5 of 6:

When to Trim Rhododendrons

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  1. Do basic pruning in spring, shaping in summer, and rejuvenation in winter. Perform maintenance pruning to remove spent blooms and damaged branches in spring or early summer (before July). [35] Shape your rhododendrons in early summer for the best chance of blooms the following year, or in mid to late winter to create a denser shrub. [36] Do radical rejuvenation in the winter (but not during a freeze) to encourage new growth in the spring. [37]
Section 6 of 6:

What’s the difference between azaleas and rhododendrons?

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  1. Azaleas are part of the rhododendron family. Rhododendrons usually refer to plants with broader leaves that bloom later in the spring and have bell-shaped flowers, while azaleas bloom earlier in spring and have funnel-shaped flowers. However, the term “rhododendrons” is sometimes used to refer to both types of shrubs. [38]
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      • Generally with pruning it's good to cut just past the point where a side shoot emerges, so the plant can continue growing without abruptly truncated branches. I think of it as looking to figure out what the plant is trying to do, and then working "cooperatively" to get the plant into the shape I want. I know they don't "think" as we do, but they do have their genetic plan and they respond to environmental cues. You'll get better results if you pay attention to that.
      • Pruning a rhododendron in winter will remove spring buds. It's best to prune after flowering. A handsaw rather than chainsaw is best for cutting larger branches.
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      References

      1. ↑ https://extension.missouri.edu/publications/g6825
      2. ↑ https://libanswers.nybg.org/faq/266485
      3. ↑ https://extension.missouri.edu/publications/g6825
      4. ↑ https://polk.ces.ncsu.edu/pruningcalendar/
      5. ↑ https://libanswers.nybg.org/faq/266485
      6. ↑ https://libanswers.nybg.org/faq/266485
      7. ↑ https://scholar.lib.vt.edu/ejournals/JARS/v64n2/v64n2-wallace.html
      8. ↑ https://extension.missouri.edu/publications/g6825
      9. ↑ https://scholar.lib.vt.edu/ejournals/JARS/v64n2/v64n2-wallace.html
      1. ↑ https://extension.umaine.edu/gardening/2022/02/16/when-to-prune-rhododendrons/
      2. ↑ https://web.uri.edu/coopext/services/ge-hotline/faq-hotline/
      3. ↑ https://libanswers.nybg.org/faq/266485
      4. ↑ https://extension.umn.edu/planting-and-growing-guides/pruning-trees-and-shrubs
      5. ↑ https://extension.umaine.edu/gardening/2022/02/16/when-to-prune-rhododendrons/
      6. ↑ https://www.uaex.uada.edu/yard-garden/in-the-garden/reference-desk/shrubs/rhododendron.aspx
      7. ↑ https://www.uaex.uada.edu/yard-garden/in-the-garden/reference-desk/shrubs/rhododendron.aspx
      8. ↑ https://extension.psu.edu/how-and-when-to-prune-flowering-shrubs
      9. ↑ https://scholar.lib.vt.edu/ejournals/JARS/v64n2/v64n2-wallace.html
      10. ↑ https://scholar.lib.vt.edu/ejournals/JARS/v54n1/v54n1-irving.htm
      11. ↑ https://polk.ces.ncsu.edu/pruningcalendar/
      12. ↑ https://scholar.lib.vt.edu/ejournals/JARS/v34n3/v34n3-furniss.htm
      13. ↑ https://scholar.lib.vt.edu/ejournals/JARS/v64n2/v64n2-wallace.html
      14. ↑ https://libanswers.nybg.org/faq/266485
      15. ↑ https://libanswers.nybg.org/faq/266485
      16. ↑ https://scholar.lib.vt.edu/ejournals/JARS/v64n2/v64n2-wallace.html
      17. ↑ https://scholar.lib.vt.edu/ejournals/JARS/v64n2/v64n2-wallace.html
      18. ↑ https://scholar.lib.vt.edu/ejournals/JARS/v64n2/v64n2-wallace.html
      19. ↑ https://ipm.missouri.edu/MEG/2018/1/cleaning_pruning_tools/
      20. ↑ https://extension.umaine.edu/gardening/2022/02/16/when-to-prune-rhododendrons/
      21. ↑ https://extension.umn.edu/planting-and-growing-guides/pruning-trees-and-shrubs
      22. ↑ https://scholar.lib.vt.edu/ejournals/JARS/v64n2/v64n2-wallace.html
      23. ↑ https://extension.psu.edu/how-and-when-to-prune-flowering-shrubs
      24. ↑ https://libanswers.nybg.org/faq/266485
      25. ↑ https://scholar.lib.vt.edu/ejournals/JARS/v34n3/v34n3-furniss.htm
      26. ↑ https://polk.ces.ncsu.edu/pruningcalendar/
      27. ↑ https://scholar.lib.vt.edu/ejournals/JARS/v64n2/v64n2-wallace.html
      28. ↑ https://scholar.lib.vt.edu/ejournals/JARS/v54n1/v54n1-irving.htm
      29. ↑ https://plants.ces.ncsu.edu/plants/rhododendron/

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