I live in SE Michigan and have 3 lovely Annabelle hydrangeas in my front flower bed, facing East. They are about 6 years old. Last year, I noticed that one of them did not develop leaves or blooms on about half of the plant (on the right in photo). The other half of the plant seemed fine, as well as the other 2 plants. I trimmed them back by about 2/3 as usual in late fall. This spring, the plant now only has leaves on a couple of stems, and the middle plant next to it seems to be suffering, with many leafless stems. I looked closely at the leafless stems and there appear to be rice-shaped brown specks or bumps all over them. They almost look like black seeds.
Does anyone have any idea what this is? Is this some sort of infestation? What can I do? I am thinking of cutting both plants down to the ground to prevent spread to the third plant. Any suggestions? I have struggled to find what it could be in online searches. I appreciate any help or advice!!
Well, I tried but the pictures are too far, not clear enough and the wood is decomposing (has many colors). All that is making it hard to find the bumps from here. Could you please take a few more pics closer so they will be crisp when I try to enlarge? Thanks in advance, Luis
That is just the outer bark decomposing. It suggests that the stem has been dead for a while so feel free to prune these stems down to the ground level.
In very northern areas, you can prune all the way down any stem that does not leaf out by mid to late May (Juneish if close to or in Canada).
Do you think you can remember exactly when did you trim them in the Fall? What month and what part of the month (early, middle, late)?
Unfortunately I did find some leaf tier caterpillars on the leaves of the largest hydrangea! Would this type of infestation cause the dieback that I am seeing?
Since your winters are much colder than my -2F Februarys, pruning early or cold winters might cause stems to die. Pruning can make hydrangeas go into "grow mode" and that makes stems sensitive to cold temperatures or early frosts.
To see which is the cause, do not prune at all in the Fall 2021/Winter 2021-2022/Spring 2022. Just observe if there is leaf out by the end of May 2022.
If 2021 stems are alive in May 2022 then pruning early was the problem. Otherwise, cold winters are to blame. If winters typically damage the stem, you can always prune the stems to the ground after the plant loses its leaves in the Fall. I try to maintain last year's Annabelle stems because old stems are woodier and will flop less after flowering.
