Cutting Hydrangeas back hard in late winter will remove the flowering buds
I believe your advice about how to prune Hydrangeas is incorrect. Cutting Hydrangeas back hard in late winter will remove the flowering buds. Flower buds form the year before they bloom. from a Master Gardener
Some hydrangeas bloom on new growth and should be pruned in late winter or early spring, before the shrub begins active growth.
These include several varieties that have become quite popular: Limelight, Quickfire, Burgundy Lace, as well as the classic "snowball" types, such as Annabelle. PeeGee also can be pruned in late winter.
Most of the other hydrangeas should be pruned in summer, once they have finished blooming. Most of these bloom on what's called "old wood" — growth from the year before. If you prune them in early spring, you risk cutting off the dormant flower buds. By pruning right after the blooms have faded, you allow the plant time to set buds for the next year. Examples of these varieties would be Oakleaf and bigleaf Hydrangea including Nikki Blue. Hydrangeas that are ever-blooming varieties such as Endless Summer actually bloom on both old and new wood can be treated the same and pruned in summer.