What is making the leaves curling by up on hydrangeas?

Curling leaves on hydrangeas can be caused by several factors, including environmental stress, pests, or disease. Overwatering or underwatering can lead to stress that causes the leaves to curl. Additionally, infestations from pests like aphids or spider mites can damage the foliage, leading to curling. To address the issue, inspect the plants for pests, check watering practices, and ensure they are receiving appropriate sunlight and nutrients.