Why are my hydrangea's wilting and drying up? They came on strong and straight this spring but have since began wilting and drying up.
Pull back the mulch and check the moisture levels on the soil.
This looks like it could be due to either lack of water or poorly draining soil and root rot.
Mulch is good to help with moisture control and keeping the plants cool, but it should be back about 6 inches from the base of the plant.
I would trim away the dead plant material and review the care information in the link below. Make the watering corrections and see how the plant responds.