Q: I want to ask what has caused die back on my rhododendrons? Some of them are 28 years old. I noticed yesterday that many rhodies in the area have some dieback. Will they come back? Or should I cut back all the dead branches? —A.H. Williamsburg
A: This is a very timely and pertinent question, A.H. I am sorry to hear this happened to your 28-year-old rhodies. They almost become part of the family when they have been with you that long.
I consulted with other Master Gardeners and local nurseries, and yours is a question on many people’s minds. There are a couple of possible contributors to this year’s surprisingly significant rhododendron damage.
Do you remember the rare windstorm that walloped us with winds gusting up to 70 miles per hour some weeks ago? That storm was likely a contributor to at least some of the damage you see. The almost-hurricane strength wind was coupled with freezing cold temperatures. This combination created a double whammy too strong even for many rhododendrons shielded with sprays designed to protect them from winter’s cold. In all my 20-plus years here in the Valley, I have never seen such a frigid combination.
Another possible cause is attributable to the situation where snowpack reflects sunlight onto the rhododendron leaves and warms them during winter days. After this brief daytime thaw, the sun sets and the temperature drops to or below freezing causing the thawed leaves to freeze.
What to do? Check the buds and branches for life. Temperatures are now warm enough that you should be able to see what is dead and what is alive. Also, did just the front of the rhodies get impacted? Another sign of windburn is when only the exposed area is impacted.
If the buds, leaves, and branches are indeed confirmed dead, then they will not come back and they need to be taken out. Sadly, there is no magic fix for this type of severe desiccation. Cut back the dead branches partially until you get to live wood. Live wood has a green tint to it. You can also gently scrape the side of the branches to observe if live, green wood is underneath as a clue to where you should stop cutting.
You may want to consider getting a professional opinion about appropriate cutback and/or removal of your rhododendrons as after 28 years I expect they are quite large and significant pruning or removal would likely have a large impact on your yard. You will need to decide what your goal is for the area where the shrubs exist. If they are only partially dead, is it worth saving the rest of the plants? Will the remaining aesthetic work for you? Will the plants still be viable?
On the positive side, this could this be an opportunity to try a new variety of rhodie that has come out in the last 20 years and that may bring a new look and joy to your yard.
Thank you for this great question, A.H. Best of luck and thanks for asking a (local) master gardener.
Have a gardening dilemma? Please send questions, along with your name/initials and community, to the Western Massachusetts Master Gardener Association at AskAMasterGardener@wmmga.org. One question will be answered per week. wmmga.org