Experts and BHG readers answer.
Hydrangea not blooming
There are several reasons why hydrangeas don't bloom. Check this list for possible adjustments to make and see if your plants recover to full bloom. It gets too little sunlight. It's planted where winter temperatures kill the flower buds (plants can still look healthy). It's the wrong variety for the region. Some kinds of hydrangeas are less cold-hardy than others. It was pruned at the wrong time. If you prune in late summer, fall, or winter you're probably pruning away the flower buds. Prune bigleaf hydrangea (Hydrangea macrophylla) right after blooming; prune smooth (H. arborescens) and panicle hydrangeas (H. paniculata) in early spring. It has been given too much or too little fertilizer.