The best advice for hydrangeas is to consider their mature size. Locate them in an area they won't outgrow and require heavy pruning to keep them in bounds. Hydrangeas do not require strict reqular pruning; simply keep them healthy by removing dead wood and they will grow and flower well.
What happens if you don't cut back hydrangeas?
Hydrangeas that bloom on old wood do not need pruning and are better off for it. If you leave them alone, they'll bloom more profusely the next season. ... Just remember new growth may come, but that new growth will be without blooms next season.
Do hydrangeas need to be cut back for winter?
Hydrangeas bloom either on old wood or new wood, depending on the hydrangea type. New-wood blooming hydrangeas should be cut back in late winter before new growth begins, while old-wood bloomers require pruning right after flowers fade in late summer.