I have several large mature rhododendrons around my house that are about 30 years old. Over the past year one of my largest with red flowers in my front yard started to die. Is there anything I can do to save them?
As the leaves wilted and turned brown, I pruned them, but now there's barely anything left of it. The younger one next to it seems unaffected. Now another one with white/pink flowers in my backyard is starting to do the same wilting.
From the photos you submitted, I see a couple of problems along with some sunburn as you mentioned. Rhododendrons aren’t meant for bright hot sun, so the heat dome in 2021 as well as our hot summers have not been kind to them.
Rhododendrons have a pretty shallow root system, so they do need water now that our summers have become hotter and drier. A nice soak every couple of weeks in the morning or more when it is hot should help keep them hydrated.
As to the dying branches, I hope they are not a sign of phytophthora root rot. This is a disease that cuts off the water to all parts of the plant above the infection and travels through the soil. I would go ahead and trim off the dying branches and let the plant work on recovering if it can.
I too have 30-plus-year-old rhododendrons and we have lost several to the heat and not watering. We didn't used to have to water rhodies in the summer, but that was before climate change and now we must give them some extra help to replace the rain showers we used to get in July and August.
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