Hydrangea Leaves Turning Yellow

Question: Please help! My limelight hydrangeas are steadily turning yellow and whole branches appear to be dying. I've never had this happen before and they've been in this location for three years.

responder: Mary Beth B.  Replied June 21, 2024, 10:23 AM EDT
response: Hi Eleanor,  I have to put on my detective hat for this one, so I have lots of questions!  When did you first notice the yellowing of the leaves and dieback of the twigs? Is this happening throughout each plant or just in one section (for example, the top, the bottom, one side)?  Have your been watering the hydrangeas? If so, how much and how often?   Have you fertilized them? If so, when and with what?  Did you use an herbicide in the vicinity, or might a neighbor have used one?  Did you make any changes or do any digging that might have affected the roots, the drainage or the amount of sunlight the plants receive?  Any information you can give me will be helpful. If you can send me an additional photo or photos of the affected plants from far enough away that I can see the plants in their entirety, that may also help.  Since one possibility is that tiny insects may be boring into the branches, I would cut out and destroy the dead and dying twigs.

responder: The Question Asker Replied June 21, 2024, 11:15 AM EDT
response: Hi Mary Beth, thank you so much for getting back to me. I've attached some more pictures of the hydrangea plants, as well as a serviceberry tree that I noticed is also developing yellow leaves and a viburnum (all in the same bed). My dogwood tree right next to the hydrangeas, however, appears unaffected.  I have not been watering the hydrangeas and usually do not unless they look very wilted. I do have a soaker hose on them this morning though (out of desperation!). They've survived July and August temps fine, so while this heat wave is unusual for June it isn't necessarily abnormal temps for them. They are not wilted in any way.   As you can see from the pictures of the full plants, the yellowing leaves are all in the understory of them, but now are starting to spread.  There are no neighbors with gardens nearby. They are fertilized with a granular holly-tone fertilizer in the spring and also have compost laid down on the spring, followed by mulch. The viburnum and serviceberry just had the compost (no fertilizer) this spring.   No change to the environment as far as I can tell (no digging, tree-trimming, etc.).   Hopefully that info helps you more - I so appreciate your time in figuring this out!  Eleanor      On Fri, Jun 21, 2024, 10:23 AM Ask Extension <<personal data hidden>> wrote:

responder: Mary Beth B.  Replied June 21, 2024, 3:59 PM EDT
response: I can't see the new photos (not sure why), but the fact that other species in the same bed are also experiencing yellowing leaves leads me to think there might be an issue with the roots or the soil.  The first thing that comes to mind is voles. They can damage roots and affect a plant's ability to take up water and nutrients. Here's some information on voles that may be helpful: https://extension.umn.edu/planting-and-growing-guides/vole-damage  Here's some guidance on identifying mole damage: https://icwdm.org/species/rodents/voles/vole-damage/  It's also possible the plants are deficient in nitrogen or another nutrient. It might be wise to do a soil test to determine whether some additives are needed. The Ohio State Extension has a great fact sheet on soil testing that includes a list of suggested labs: https://ohioline.osu.edu/factsheet/hyg-1132  Leaf scorch can also cause hydrangea leaves to turn yellow and then brown, but that usually happens to the leaves on the top of the plant or the ones that are closest to the sun. That doesn't appear to be the case with your shrubs. Regardless, I suggest making sure the plants are getting enough water, particularly during this hot spell. Hydrangeas are water lovers (the name comes from hydros, or water), so they need about an inch of water every week to thrive.  If none of these suggestions help, you might want to send a sample of Ohio State's plant and pest diagnostic clinic for analysis. Information on the clinic and on submitting samples is here: https://ppdc.osu.edu/  I wish I had a handy solution, but unfortunately diagnosing plant problems isn't always simple. I hope you can determine the cause of the problem and get those plants healthy again!

responder: The Question Asker Replied June 25, 2024, 11:13 AM EDT
response: Thank you for your help!  On Fri, Jun 21, 2024, 3:59 PM Ask Extension <<personal data hidden>> wrote: