Depends on the variety - if its a macrophylla type (mophead or lacecap) you don't prune, basically - you wait till April when its starting to grow, then remove any dead flowerheads and obviously dead shoots, and that's it,otherwise you lose flowers. If its got too big, you can prune out some of the branches to the ground in spring, leaving others alone, and those will produce flowers, usually larger ones.

If its a paniculata type (cone shaped flowers) you can cut those down in late autumn, or prune back as much as you need to and it will still flower.

yes as bamboo says it depends on the type you are growing. Her advice is spot on.

welcome to GoY too.

My gardener "did me a favor" and pruned my Hydrangea Macrophilla last autumn. I had no flowers this summer. He cut off all the dormant buds. Yes some varieties bloom on new wood also, but the biggest & best blooms come from the buds set the previous year. Those are the ones you really want.

That is the way it is done around here. Hydrangeas line the rural roads, and the ones that bloomed this year get cut down to the height of the stone wall behind it - using a chainsaw. The ones that were done this last spring didn't flower, but had lots of leaves and will flower next year. The tourists are always stopping to take photos.

I can see that would be the best way to manage in that situation, its a bit like hedging, Wylie... but one or two specimens in a mixed planting setting means not wanting to lose flowers