Hello Linda,

Thanks for reaching out to the UNH Extension Infoline. You could be right- heat stress is a real thing for many of our garden plants and we've had quite the hot summer so far. Are your hydrangeas irrigated? If not, it could be a water issue as well.

That being said, I would also recommend getting a soil test to make sure your soil has the right pH and nutrient balance. For more information about getting a soil test, visit our Soil Testing Services website.

The other possibility could be disease but I would start with the soil test first. If the soil test comes back as not showing any issues, I would send in a plant sample to the Plant Diagnostic Lab. Find more information about the lab and how to send in plant samples here.

I hope this helps and feel free to ask if you have further questions!