Hydrangea dieback - Ask Extension
Almost all of our Nikko blue type hydrangeas including Endless Summer varieties, have died back. There is now growth at the base, but the stems are al...
Knowledgebase
Hydrangea dieback #790284
Asked May 11, 2022, 3:11 PM EDT
Almost all of our Nikko blue type hydrangeas including Endless Summer varieties, have died back. There is now growth at the base, but the stems are all dead. Some of the plants are large, that we've had for a number of yrs. but others were just purchased last year. Same goes for our rhododendrons. Lots of dieback on some of them and they didn't set many buds. Can you tell me what is going on? We have one large variety rhododendron called Scintillation, that always has beautiful flowers every year, but not this year. I had to cut out lots of dead branches on another large rhody. This is the first time in the 30+ years we've lived here that we've had anything like this occur. I've included a pic of what the Scintillation looked like in the past. Thanks, Jack
Allegany County Maryland
Expert Response
Your garden is beautiful, and we understand your concern.
In the case of your Hydrangea, it was winter damage that has caused dieback. Even in milder areas of central Maryland the winter temps were cold enough to kill many branches and some, all the way back to the ground.
If you are certain that the branches are dead, you can prune them out. (Mine were somewhat late to show any leaf buds).
Your Nikko Blue hydrangeas bloom on wood made the previous season, so you won't have flowers on them this year.
You Endless Summer however, are newer cultivars bred to be re-bloomers. They bloom on wood made the previous year, take a break and then try to bloom again. The first set of those blooms are lost to the cold, but you may see some blossoms later into the season. (I will say that mine have not lived up well to their hype.)
One winter I actually completely lost the mature shrubs, but where the larger branches had rooted to the ground on their own (in previous years) they lived and re-grew into replacements.
For your Rhododendrons, some of your damage could be cold-related, including damage to flower buds and, winter burned, scorched-looking leaves but we wonder if there may be more going on, particularly with age.
Take a look at this page to compare with what you are seeing:
https://extension.umd.edu/resource/botryosphaeria-canker-shrubs Botryosphaeria canker disease can commonly cause some scattered dieback on older specimens. Here is a page that explains it: https://extension.umd.edu/resource/botryosphaeria-canker-shrubs
You can prune out dead wood on a dry day, about six inches below the damage. These shrubs can take severe pruning and come back if they are otherwise healthy.
This page covers other issues this plant family (which includes azaleas) can have:
https://extension.umd.edu/resource/azaleas-and-rhododendrons-identify-and-manage-problems
Given how long you've had them we assume that the Rhododendrons were only pruned (if at all) just after they bloomed. Later in summer you'd be cutting off the future flower buds. Another thing to think about is how much light older plants receive. They do best with partial (morning ideally) sun. Sometimes as our gardens mature there are changes in how much shade or root competition comes from other shrubs and trees.
Christine
In the case of your Hydrangea, it was winter damage that has caused dieback. Even in milder areas of central Maryland the winter temps were cold enough to kill many branches and some, all the way back to the ground.
If you are certain that the branches are dead, you can prune them out. (Mine were somewhat late to show any leaf buds).
Your Nikko Blue hydrangeas bloom on wood made the previous season, so you won't have flowers on them this year.
You Endless Summer however, are newer cultivars bred to be re-bloomers. They bloom on wood made the previous year, take a break and then try to bloom again. The first set of those blooms are lost to the cold, but you may see some blossoms later into the season. (I will say that mine have not lived up well to their hype.)
One winter I actually completely lost the mature shrubs, but where the larger branches had rooted to the ground on their own (in previous years) they lived and re-grew into replacements.
For your Rhododendrons, some of your damage could be cold-related, including damage to flower buds and, winter burned, scorched-looking leaves but we wonder if there may be more going on, particularly with age.
Take a look at this page to compare with what you are seeing:
https://extension.umd.edu/resource/botryosphaeria-canker-shrubs Botryosphaeria canker disease can commonly cause some scattered dieback on older specimens. Here is a page that explains it: https://extension.umd.edu/resource/botryosphaeria-canker-shrubs
You can prune out dead wood on a dry day, about six inches below the damage. These shrubs can take severe pruning and come back if they are otherwise healthy.
This page covers other issues this plant family (which includes azaleas) can have:
https://extension.umd.edu/resource/azaleas-and-rhododendrons-identify-and-manage-problems
Given how long you've had them we assume that the Rhododendrons were only pruned (if at all) just after they bloomed. Later in summer you'd be cutting off the future flower buds. Another thing to think about is how much light older plants receive. They do best with partial (morning ideally) sun. Sometimes as our gardens mature there are changes in how much shade or root competition comes from other shrubs and trees.
Christine
Christine,
Thank you for your quick response. My wife and I live on 10 acres of our mostly wooded property here in Lavale, in Allegany Co. We’ve been here since the early ‘80s and I’ve always had an interest in rhododendrons and gardening in general. (One that I planted years ago, is about 15’ x 25’). I wanted to mention to you about something else that has occurred here: the invasion of Japanese stilt grass and the disappearance of our once plentiful May Apples. Also, we have many Ash trees, which, unfortunately, have died due to the emerald ash borer. The only good thing I can say about that is that ash makes good firewood.
I agree with you that the endless summer hydrangeas have been over-rated. They sell them at Lowes and Walmart here. I got some on sale last year and every one of them died back. I have a few panicle hydrangeas like Limelight and Little Lime, etc that do much better here. The only pruning I do with rhododendrons is removing the old flower heads. (when I can reach them). That’s all, except for removing dead limbs.
The biggest problem I have here, without a doubt, is deer. They browse on anything and everything. I learned early on that we needed a high fence around the vegetable garden, but spray deer repellent on things close to the house. Everything else is pretty much fair game for them, so try to plant things they don’t like. Well, I’m running on. Good talking with you.
Jack
From: Ask Extension
Sent: Thursday, May 12, 2022 11:29 AM
To: oldpoo
Subject: Re: Hydrangea dieback (#0060215)
Your yard sounds lovely. It's beautiful out there.
The Endless Summer Hydrangea can be beautiful but our weather has become more unpredictable. It's the so-called re-blooming part that hasn't been all it's cracked up to be for me.
Japanese Stiltgrass has become an invasive headache everywhere it seems.
And deer.... if we didn't have dogs I wouldn't have half the plants near my house that we do. I am making some headway in planting some native plants that can compete.
Pages on each of these if you're interested:
https://extension.umd.edu/resource/japanese-stiltgrass-home-landscapes
https://extension.umd.edu/resource/deer-damage
this one includes a list of native, deer resistant alternatives.
Christine
The Endless Summer Hydrangea can be beautiful but our weather has become more unpredictable. It's the so-called re-blooming part that hasn't been all it's cracked up to be for me.
Japanese Stiltgrass has become an invasive headache everywhere it seems.
And deer.... if we didn't have dogs I wouldn't have half the plants near my house that we do. I am making some headway in planting some native plants that can compete.
Pages on each of these if you're interested:
https://extension.umd.edu/resource/japanese-stiltgrass-home-landscapes
https://extension.umd.edu/resource/deer-damage
this one includes a list of native, deer resistant alternatives.
Christine
