Sorry t hear this, Suggi. If you have voles, you should confirm that they are to blame by looking for the "runways" that these pests create when they dig close to the top of the soil. They do not like being in open and stay digging pretty close to the roof of the soil line. Thus, I would look to see if you can detect vole activity very close to the soft bark of hydrangea, where the stems meet the soil line.

If you do not detect these runways, the mystery deepens. If you detect the runways near the base of the hydrangea, they probably have gnawed on this hydrangea's bark and-or roots and whether it recovers will depend on whether the shrub can recover on its own and whether the voles stay away and cause no more damage.

You can always carefully remove the roof of these runways that they build, insert a mouse trap with peanut butter and cover the trap with an upside down box. I would make upside down "U" shaped cuts on the ends of the boxes so they do not topple these roofs & cover any places where light can get into the runways.

You can also try wrapping hardware cloth around the base of the shrub (to build a fence) and/or separate the mulch from the plant base (say 4" or so) so they will have to be exposed if they want to gnaw on the stems... something they just do not like.

If you put a mouse trap and catch one, put it back again to check for more. Some people will add a piece of fruit (apple, say) before adding back the mouse trap... to see if the fruit is gnawed, an indication that there may be more pests.

Damage by voles usually results in localized wilting of leaves. Only the leaves that got water from gnawed roots are affected. The other unaffected parts of the bush will stay fine. The damage is not going to get better if the plant cannot recover on its own, something that will take a long time so, you may have a browned out section and an "ok" section of this hydrangea tree. I have not heard of this happening with a hydrangea tree before so I am not sure if you should wait it out or cover your loses. In the cases I have heard of, the persons took action against the voles and replaced the affected shrubs. Voles can injure hydrangeas, hostas and even roses.

Luis

Thanks Luis

Guess what - I was able to actually pull the hydranga out of the ground as it had no roots left at all. Unbelievable.

What do you think of the castor oil. I do not dare put out covered rat traps as I did so last year with a little peanut butter on them for chipmunks and got them but all that were left were the feet from other animals taking the covers off and taking away the chipmunks. Also, one time (the very last time I tried it) I woke up to a possum with his head in the box and his snout in the snapped trap. Boy, did I ever freak out. I called an exterminator to come and get the darn thing --- there goes $75.