Q.How Do I Prevent My Hydragea From Getting Worms Inside The Leaf Clusters In The Spring?
I live in southern Ontario. In the spring my hydrangea get small worms that seal the forming leaves shut and then eat the forming flowers inside the leaf cluster. How do I prevent this? I usually squeeze each leaf cluster to kill the worm inside and then pull the leaves open.

Certified GKH Gardening Expert
Ah! Leafrollers... Terrible.
The best way to kill these guys off for good is to infect them with Bacillus Thuringiensis. This common bacteria is harmless to us, but detrimental these pests, (AND MOSQUITOES) so it is a safe option, environmentally.
Here are some articles that will help:
https://www.gardeningknowhow.com/plant-problems/pests/insects/leafroller-damage-control.htm
https://www.gardeningknowhow.com/plant-problems/pests/pesticides/using-bacillus-thuringiensis.htm