When and how do you prune hydrangeas?

Cut them right down about 4-5 inches from the dirt around Oct, Nov Dec I Live In Ca. and they return huge every spring I also spray all my plants every 3 months with Schultz that comes in a bottle that Connects to a gun sprayer that Connects to your hose. Check out Home Depot or Lowes. Dont be afraid with you hydrangias.

Depends on the type of hydrangea....if it's woody you can't cut it to the ground...just trim it to the size you want...I do mine in the fall or early spring (Minnesota),,,,if the hydrangeas are herbaceous you can cut them to the ground and they will come back.

I live in Pennsylvania and I wait until Spring when the first leaf buds start. Look for the dead stems with no new growth, I cut them to the ground. This helps to thin it out, also. Then just let it go!

After looking at the 3 answers you already received, my suggestion is follow all of them. Go easy where they are woody if you have a lot that is woody. If not follow #1. If that doesn't work well then go for # 2. All are good. Flowering shrubs are " managed " after they bloom.

Overgrown like lilacs do best thinned 1/3 a year until you have them where you want them. Over cutting/thinning weakens the shrubshrub. Good luck!

Hydrangeas can be pruned after they bloom.

after they bloom & no more than 1/3 of the plant. pruning too much leaves them weak

Here's a helpful post on how and when to prune hydrangeas: https://www.hgtv.com/outdoors/flowers-and-plants/trees-and-shrubs/hydrangea-care-to-prune-or-not-to-prune-your-hydrangeas