· Brent Wilson's Answer
· This is a very good question. I've been through the same thing this summer here in zone 8a (mid-Georgia). It's been a long and hot summer and is showing us which species (types) of hydrangea can handle the heat, and which ones can't. Sometime in July, my Hydrangea arborescens (Annabelle, Incrediball, and Incrediball) started severely wilting every day, even when I watered them deeply every morning. It got so bad they started to drop foliage, so I cut them halfway back to try to save them. All three varieties died. I won't replant any of the arborescens species. These are probably best suited for up north? As long as I water them every day, my French-type hydrangeas (macrophylla species) have all survived without much wilting, but they didn't produce many blooms. My Endless Summer hydrangea bloomed once and not again but looks healthy. The hydrangeas that have handled the heat the best are the Oakleaf's and the Pee Gee's (paniculata). They bloomed as normal and didn't wilt much as long as I gave them some water every day it didn't rain, which has been many. So, for those of us in the South, I think it comes down to the species (type) of hydrangea? And like I said previously, this long and exceptionally hot summer has shown us which varieties can take the heat and which cannot. Not sure what type of hydrangea you have but we're so close to fall that I'm not sure I'd recommend cutting them back now. Otherwise, if you do cut them back, they might not bloom next year.
Here's a link to an article that provides instructions for pruning the different species of hydrangea:http://www.gardenality.com/Articles/338/How-To-Info/Pruning/How-To-Prune-Hydrangeas/default.html
I'm gonna wish us both better luck next summer with our hydrangeas. I think I'll plant more varieties of Oakleaf (quercifolia) and Pee Gee (paniculata) hydrangea species in my garden this fall. I like them better anyway:-))