Answering questions about azaleas

Published 3:39 pm Wednesday, April 3, 2024

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I get these calls from time to time and there are several answers to the question, “What happened to my azaleas?” It’s one that takes a few more questions to get to the bottom of the problem.

The first question I ask in return is, “What are they doing?” The first caller has one azalea out of several that has bloomed but turned brown. There are a few things that can cause this, the first of which is frost. Some azaleas put on new growth before they bloom. This new growth is not going to be hardened off to the cold at all. When it gets cold like it did a few weeks ago, this bush was probably further along than the others or maybe not in a protected area. I have seen this happen in my landscape this season.

Another possibility can be the azalea lace bug. I have done previous articles on this pest. The leaves begin to have a dull, stippled look on the upper leaf surface and black spots on the underside. These are symptoms of the azalea lace bug.

Lastly, there could be a root-rot issue that has killed the plant but there was enough energy left for one last hoorah. In this case, we can dig it up and take a look at the roots. Often, they will be rotten and emit a rotten odor. There are tests that can confirm the root rot but even if confirmed, there isn’t a treatment that will bring the plant back.

While it isn’t possible to prevent these things from happening, maintaining a healthy azalea is the best way to minimize damage from pests, disease, and even environmental issues such as frost.

Remember azaleas like a lower pH so make sure to have the soil tested every two to three years. Use acidic fertilizer such as ammonium sulfate (21-0-0) for your nitrogen needs if recommended on the soil test. Fertilize azaleas after the spring bloom and not before the last frost. This can minimize frost damage. Make sure not to fertilize after August, this could delay dormancy and cause brown leaves to be there all winter.

The second question is, “Why have my azaleas bloomed at the bottom and not the top?” This is a great question and opens us up to either operator error or environmental conditions. First, we’ll discuss operator error, a.k.a. pruning time. Any plant that blooms before Memorial Day is most likely blooming on last year’s wood. This means that those flower buds take an entire season to develop. If a plant is blooming after Memorial Day, then it is most likely blooming on new wood. This means that the blooms form on this season’s new growth. This is important to know because when you prune may have quite a bit to do with whether or not you have blooms this season.

In the case of azaleas, they are mostly spring bloomers on old wood. This means that they should be pruned for shaping and air-flow right after the blooms drop. If pruned in the fall or winter, you probably pruned this season’s blooms right off. Some azaleas are season long bloomers. In this case it is still best to prune prior to June 1 or right after the spring bloom is finished. Shaping can be done throughout the summer but this only removes the longer new growth, not the entire outer edge of the shrub.

The second issue here could be that cold snap/frost we got in early March. Being a warm January and February, we were ahead of schedule for most plants. Many of our azaleas were just before blooming when that frost occurred. I have probably close to 25 azaleas around my house and I watched many of them this year to see when the blooms were going to come out. I have several that are in direct sun all day, which were days from blooming when that cold snap came.

Being in an exposed location, these bushes were really ahead of schedule and had the same issue with the tops not blooming but the bottoms did. I had others that were also close to blooming but located under trees which bloomed just fine. The bloom is staggered with some early bloomers and some later bloomers. The later bloomers still had tight buds when the frost occurred, they turned out just fine. So, this has to do with location and cultivar or variety as well.

Where our plants are located has so much to do with their health and bloom. For example, Southern exposure allows the plants to receive the most sun all day but also makes them vulnerable to the first rays of sun on cold mornings. This is when the most damage can occur. If there is frost on the plant the cells are frozen too. As the sun warms the tissue, the cells will burst if warmed too quickly. This can happen this time of year on young fruit trees or any young smooth-barked tree. I have camellias on the eastern side of my home and directly beside the house on the southern side. I lose the blooms on the eastern side to frost much quicker than I lose them on the southern side because they are more protected from the sun until the frost is able to melt. Of course, we always want to go back to the idea of Right Plant in the Right Place.

If you are having trouble with growing in your home landscape, call the Extension office at (252)946-0111 or email me at Keep an eye on our website or the Beaufort County Master Gardener Facebook page for upcoming classes and events. Mark your calendars for our Totally Tomatoes class April 13 (registration required, only four tickets left) and our Extension Master Gardener Plant Sale April 20. We will have over 1,000 vegetable seedlings for sale from 9:00-11:00 a.m. or until supplies last. Until then, Happy Gardening!