To have beautiful hydrangeas it is best to learn not to intervene too much on them: often people overdo it and you see them pruning the plants down to ground level every year. The most common varieties (such as macrophylla and serrata) bloom on the previous year's branches.
It is therefore best to limit yourself to removing only the oldest and most unruly branches, at most one third of the total, at the end of winter, and to remove only the dried flower on the others.
Other species such as paniculata and arborescens can be pruned more drastically because they bloom on the current year's branches. Climbing varieties, involucrata and quercifolia can also be left unpruned, unless to give the plant a more tidy overall appearance.
