Help Identifying Hydrangea Tree Disease

Asked August 20, 2020, 12:34 PM EDT

Hi, We have a Hydrangea Tree that has a problem with some limbs. The "sick" limbs show stunted growth with smaller leaves and blossoms (or no blossoms at all). I applied medium pressure on one of the limbs in question and it snapped off easily. I have attached pictures for you to examine. If you can help us identify the problem and suggest treatment options, we would greatly appreciate it. We sure would hate to lose this beautiful tree. Thank you!

Guilford County North Carolina

4 Responses

I have a few questions that will hopefully help me determine what's going on.

  • When did you notice this problem?
  • Has there been any damage to the plant? (wind, hail, lawnmower, weed whacker, etc)
  • Where does the damage begin? Is it just a branch/branches or does it go all the way back to the main trunk?
  • Are there any holes or anything you can see on the trunk or affected branches?
Would it be possible to get another couple of pictures a little more close up of the affected parts?

Thanks,

Hi, Hanna. Sorry for the delay getting back.

We moved to this home in December of 2019, so this is our first experience with this tree. That said, we noticed the problem when the foliage started in the spring. It was clear that the affected branch didn't have the same vitality in terms of fuller leaves and growth as the rest of the plant.

There has been no prior damage to the tree that we are aware of. I personally care for the yard and there has not been any event that I have witnessed.

The damage is with just one branch (and the connecting branches to that branch) which stems from the upper trunk.

I can't see any obvious holes or damage/fungus on the tree or branches or trunk. However, the affected branch is brittle and easily broken (normal for hydrangea??). The wood inside seems too dry and the very center core of the affected branch is black in color and the black substance in question appears dry and falls out of the core in little "granules".

I'm not sure of the tree's age, but suspect it is many years old. Perhaps it is just losing it's vitality and dying? I also must admit to not having any experience with hydrangea trees so don't know what is normal and what is not. I can see evidence of significant past pruning which could indicate the problem predates this year, or again, perhaps this is normal maintenance for this species. Not sure.

If you need more pictures or information, please let me know. Thank for your help, Hanna!

Regards,
Tony

Thank you for the additional information and pictures. What I have narrowed it down to is either a root rot, a vascular wilt, or maybe southern blight. With only part of the plant wilting and dying that is why I have narrowed it down to those 3.

Vascular wilts clog up the plant's vascular system and will cause similar symptoms, but with the stem cross-section, it doesn't quite look like the vascular system is affected, just the center portion, or the pith, which I can't seem to find anything that affects hydrangea pith. That may just be secondary decay.

Root rots, particularly phytophthora, can cause similar above-ground symptoms as well. If you are able to dig up and look at some of the roots that will give you a better idea if it's root rot. Here is some information on what to look for: https://ag.umass.edu/landscape/fact-sheets/phytophthora-root-crown-rot

Southern blight can affect hydrangeas and can cause part of the plant to look wilted, but I am tempted to rule this one out because it really doesn't start to show symptoms until hot weather sets it, and if you noticed the problems when the leaves emerged then this one might be less likely. Upon closer inspection of the crown and roots, you will notice mycelium and sclerotia, and if absent can rule this one out. Here is some information about southern blight and what to look for: https://extension.tennessee.edu/publications/Documents/W289-H.pdf



Thank so much for your help, Hanna! :)