Rhododendron Problems: What’s Wrong With My Rhododendron?

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Learn the common types of Rhododendron problems that may cause your normally care-free plant to be unhealthy and how to fix them.

Generally speaking, Rhododendrons are very care-free plants that don’t require much maintenance at all. (You can find more about caring for your Rhododendrons HERE).

However, occasionally you may run into an issue where your plants are just not looking up to par.

Since I’ve had rhododendrons in my garden for so long, I have run into a few of the common rhododendron problems over the years. So I thought I would share my experiences in case you run into the same problems and need some help.

Yellow Leaves

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Rhododendron with Yellow Leaves

One potential Rhododendron problem is that the leaves are turning yellow.

Epsom Salts*

According to the American Rhododendron Society, if the plant has older leaves that have turned yellow between green veins, you likely have a Magnesium deficiency. Sprinkle some Epsom Salts* around the plant to correct the issue.

Iron Sulfate*

If the same symptom appears in new leaves, then it is likely that the soil is too alkaline.  The alkalinity prevents the plant from taking in the iron that it needs to remain healthy.

For a quick fix, you can try spraying the ground and leaves with an iron sulfate* solution. While this will provide quick relief to the plant, you will probably want to look into making your soil more acidic long term. Applying some peat moss and acidic mulching materials around the plant will eventually help to bring the soil pH down.

Find out more about soil pH, testing it and changing it HERE.

Brown Spots On The Leaves

Brown spots on Rhododendron leaves

A second type of Rhododendron issue is brown spots on the leaves. There are several types of fungus that can cause this.

With the humid summers here in SC, I always seem to have at least one Rhododendron with this problem.

To fix it, I usually clean up around the plant and try to cut back a few branches to reduce overcrowding and improve the air circulation.

Although the brown spots don’t look great, they don’t seem to bother the plant much.

Stem Die Back

Rhododendron with Stem Die Back

Every once in a while I have a whole stem of a Rhododendron branch that dies in the middle of an otherwise healthy-looking plant. According to the Clemson University Cooperative Extension, this is caused by another kind of fungus that gets under the bark.

It usually attacks plants that are under stress due to drought, too much sun or late frosts.  So the plan of attack is to cut off the dead branch as soon as possible and then try to remedy the source of the stress (if possible).

Rhododendron with new shoots after the plant has died back

I had one plant last year that all of the stems eventually died back, and I thought it was dead. But then, much to my surprise, it started to grow some brand new shoots from the bottom. So there is a chance that your tough rhododendron may recover.

Curled Up Leaves

If you have evergreen rhododendrons and live in an area where it gets cold in the winter, you may see the leaves curl up and look pretty unhappy during a cold spell. Don’t be alarmed.  The leaves are just trying to conserve water in the cold, dry air.  They will open up and come back to life once it warms up.

If you see curled up leaves in the summer, though, that is a sign that your Rhododendron is much too dry. Water immediately!

Buds Don’t Open

There is nothing more disappointing than seeing your Rhododendron covered in buds and then not getting any flowers!

These are the 2 common causes of this that I’ve seen.

Bud Blast

Rhododendron plant with bud blast

Bud Blast is a fungal infection that causes the buds on the Rhododendron to die and turn black before they bloom.

It isn’t a life-threatening condition for the plant, but it is really disappointing for the gardener!

It is thought to be spread by the Rhododendron Leaf Hopper, an insect that doesn’t do much damage to the plant other than spreading this fungus around.

You can get insecticides to kill the bugs, but I prefer to just pick off the infected blooms as soon as I see them (less detrimental to the environment).  That decreases the number of fungus spores that are available to be transported and limits the spread of the issue.

Frost Bite

If you have a late frost, it’s possible that the buds on your Rhododendrons were affected.

In this case, they usually turn a light brown color and get a little mushy (for lack of a better term).  In other words, they look like they’re been frozen and thawed.

Other than covering the plant during the frost, there isn’t much you can do about this condition.  But fortunately, it usually doesn’t cause any lasting damage either. Unless you are trying to grow Rhododendrons that aren’t zoned for your area…then you might want to look for some other varieties that won’t be affected so much by the cold.

Few (Or No) Flower Buds Form

Again, there are a number of reasons why you don’t have any buds on your Rhododendrons.

Incorrect Pruning Or Deadheading

The most common cause of not having any blooms is that the plant was pruned after flowering the previous year, or too much of the flower head was removed when deadheading.  In this case, you’ll just have to wait it out until next year…and remember not to cut off the flowering stems 🙂

Too Much Shade

Too much shade can also cause fewer (or no) blooms. While most Rhododendrons will do fine in the shade, there are some varieties that like more sun. And almost all of them will produce more blooms if they get dappled shade, rather than total shade.

Incorrect Fertilizing

Too much fertilizer applied after the plant has finished blooming is another culprit of fewer blooms. First, since the Rhododendron roots are so shallow, too much fertilizer can stunt the growth of the whole plant. Second, fertilizer applied after the plant has finished blooming mostly promotes lots of leaves…so if you are going to fertilize, be sure to apply it at the correct time.

Not Enough Water

Letting the plant get too dried out or allowing the roots to get too hot will also affect the number of buds that form.  Since the buds grow during the summer, making sure that you have a thick mulch cover and that your Rhododendrons are getting at least 1″ of water per week will help it to be as healthy as it can be.

Growth On The Stems

Rhododendron bush with Lichens on the stem

Lichens are a combination of algae and fungus forming a partnership to help each other grow. Generally, they don’t actually hurt the plant that they are living on, since they make their own food.

However, if your Rhododendrons have lichens growing on them, it usually means they are thinning because of poor growing conditions, disease or old age. So you may want to take a look at rejuvenating the plant, by pruning it or improving the area around it to make the plant happier.

I have seen this on plants that have become too crowded or are lacking in Magnesium (those yellow leaves from above).

More Information

If you want even more information about Rhododendron pests and problems, this guide from Washington State University has an extensive list of Rhododendron problems and how to fix them. You can get it for free online, or buy a printed copy.

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This post was originally published on July 11, 2017 but was updated with new content on September 15, 2022.


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79 Comments

  1. We moved into a 1970’s house four years ago. They back yard has great rhododendrons that we think were planted in the 70s when the house was built because the are all over 8 feet tall. One was taking over and an oak and blocking the sun from three other rhodies. We pruned it back (a year ago) and got rid on a lot of dead internal branches. The branches literally snapped off in your hands. I was cleaning up some wind fall lodges in it this year. Their a several strange branches. All are internal to the the bush. Each of these oddities is coming off of a single branch that was pointing down. There are six to eight tightly clumped branches pointing upward from each branch. They all have leaves and are together like a bouquet, about 1.5 feet long. It looks like if I cut one and put it in dirt another rhododendron would grown from the cluster. Do you know what are? Should I leave them alone or cut them out from the middle of the bush? Thanks for any incite you can provide.

    1. Wanda Simone says:

      Hi Katy…it sounds like witches’ brooms. It’s a genetic mutation which often can be cut off and transplanted to grow a dwarf version of the plant. Unless they’re diseased, they aren’t harmful to the plant. However, they can be caused by a fungi infection, so if the leaves get spots or don’t look healthy you will want to remove them. Otherwise it’s really up to you whether you prune them or leave them (depending on whether you like the look of it or not.)

  2. AMITAVA GHOSE says:

    The buds on my Nova Zembla Red Rhododendron, for next spring are miniscule. Why?

    1. Wanda Simone says:

      Hi Amitava…it sounds like you have leaf buds and not flower buds forming. That can happen if the plant didn’t get enough water during the summer, is planted in soil that is too alkaline or is exposed to fertilizer with too much nitrogen (often happens if they are planted close to the lawn, since grass fertilizer is high in nitrogen).

  3. Amitava Ghose says:

    Thank you so much Wanda I think you are correct! Lack of moisture perhaps caused the Rhododendron not produce any flower buds for next year. Kin of sad but will correct the situation for next year.

  4. Hi there,
    My rhododendrons leaves have all turned yellow/orange are dry and sparse. It did not flower this year along with the others in the yard. There is lichen and moss on the branches. The previous owners living in this house pruned it back significantly. It is definitely dying or possibly almost dead, is there any last effort I can try to do to save it?
    Please help!
    Thanks so much,
    Cara

    1. Wanda Simone says:

      Hi Cara…you’re right, it sounds like it’s not doing too well. Usually the leaves turn yellow or orange like that when the soil is too alkaline and it isn’t able to absorb the proper nutrients. In which case, it may be possible to save it by adding iron sulfate and peat moss around the plant to help acidify the soil. However if you have other Rhododendrons in your yard that are doing well, this isn’t as likely to be the problem and it could be a fungus or disease causing the problem. If that’s the case, I would take it out so it doesn’t end up affecting the other plants in your garden.

      1. Hi Wanda,
        Thanks for your help. We may just need to cut it down. I am wondering if could also be old age?
        Thanks,
        Cara

  5. irene poole says:

    mine roddy has buds but they have not opened, hope you can help with this problem,

    1. Wanda Simone says:

      Hi Irene…Rhododendrons grow buds the summer before they bloom. So the buds you are seeing now should open in the spring. It sounds like you will have a lot of flowers then 🙂

  6. Eileen Horn says:

    I have a bed of rhododendrons & camellias and all seem to be really healthy except one – it has what looks like mildew spots on its leaves. Can you please tell me how I can treat this and will it spread to the others?

    1. Wanda Simone says:

      Hi Eileen…that sounds like a fungus. Yes, it can spread to your other Rhododendrons. I would remove the branches that have the spotted leaves down to the first set of non-infected leaves. Then rake up any leaves that have fallen under the plant. Make sure that the Rhododendron is watered well, but avoid getting too much water on the leaves. If you want to be sure it doesn’t spread, you can get a fungicide (such as chlorothalonil) to spray on the remaining leaves and the plants immediately around it.

  7. Hi Wanda…read through the posts above and I too, have yellow and thinning leaves located right next to it’s 65-year old brother which seems to be doing fine (both are about 10-12 feet high. I was wondering, there is substantial ground cover, leaves, etc under both of the plants…is it possible that the leaves and ground debris are not allowing the roots to breathe properly or keeping the ground constentantly damp? When moving the debris to expose the dirt, the ground is moist much like you would find under a bed of forest debris. Would appreciate your thoughts. Brad

    1. Wanda Simone says:

      Hi Brad…It’s possible that the extra leaf build-up is causing some issues. Rhododendrons do like moist soil but not too wet, so you might want to remove them and see if it helps. Afterwards, I would add some ground bark mulch which will help to keep the soil cool without smothering it.

  8. Verna Gurwitz says:

    My rhodo has an oval hole in the main trunk near the base. A borer?
    Should I fill the hole?
    Several branches have brown leaves. I would like to save the tree What can I do?

    1. Wanda Simone says:

      Hi Verna…It sounds like a borer. Unfortunately once it has bored into the Rhododendron, the only way to get rid of it is to cut off the parts where the tunnel is located. Everything above that point will likely die off eventually. Since your hole is so close to the base, you may not be able to save the plant. If you want to try, you can apply an insecticide that is specific to borers, which should prevent any further infestations. And if you have other Rhododendrons or Azaleas in the area, I would use the pesticide on them, so the borers won’t attack them, too.

  9. Jim Dickey says:

    I recently moved to a home with a couple Rhododendrons. They had a few blooms but most of the buds have turned brown and dried up. I did notice on one plant a lot of stickiness like cottony substance. I have been using Neemoil every 7 days as the instructions say. Does this sound lke it is an Aphid problem? The plants seem to be growing new leaves and has put on new buds for next year.

    1. Wanda Simone says:

      Hi Jim…Sorry for the late reply, I somehow missed your question. It sounds like either aphids or Rhododendron Whiteflies. The neem oil should take care of them, but it may take a few applications. Also, make sure to remove the dead buds and clean up any dead leaves to prevent disease.

  10. Mike Whitton says:

    I have tiny white insects on new sprouts coming out of large branches on my rhododendron. They are curling the leafs. What do I do. Thanks

    1. Wanda Simone says:

      Hi Mike…it sounds like Rhododendron Whiteflies or aphids. In either case, you can wash them off with an insecticidal soap, although it may take a few applications to completely get rid of them.

  11. Hi. I see a big banner about how to fix 7 rhododendron problems. The upper right photo is identical to my problem, but I don’t see how to access the information! Help!

    1. Wanda Simone says:

      Hi Lara…I’m not sure what is going on there. You should be able to scroll down and see all of the information. Maybe try reloading the page?