Thankfully, this is not a very common problem that few gardeners run into. U.S. gardeners grow four (4) species of hydrangeas: smooth hydrangea (Hydrangea arborescens), oakleaf hydrangea (H. quercifolia), bigleaf hydrangea (H. macrophylla), and panicle hydrangea (H. paniculata).

There are five reasons why some hydrangeas don’t bloom:

1. Type of hydrangea… Bigleaf hydrangeas, those that produce blue or pink flowers, are the most troublesome. Lots of cultivars are available, some that are very winter hardy and others not so much. If winter temps in your region are extremely low, plants may die back to the snow line or to the ground. Bigleaf hydrangeas bloom on both old (last year’s) and new (current season) wood. Loss of the old wood results in your hydrangea blooming only in late summer on current season’s wood. No flowers may mean that the variety that is not reliably hardy in your zone.

2. Not enough sunlight… The site should receive 3-6 hours of direct sun daily. Panicle hydrangeas require the most sunlight and oakleaf hydrangeas and smooth hydrangeas as little as 2 and 3 hours daily respectively. As a rule, more sunlight means more flowers.

3. Pruning at the wrong time…  Generally, hydrangeas don’t need pruning other than to control plant size and to remove dead wood. Pruning time is most important. H. macrophylla and H. quercifolia plants are pruned in early summer or in late winter; H. arborescens and H. paniculata are pruned in late winter to early spring before new growth begins. Don’t cut plants back too far. If your hydrangea won’t bloom, skip pruning any time. You may be overpruning.

4. Too much fertilizer… Overfeeding your hydrangeas particularly with too much nitrogen (N) or not enough phosphorus (P) in the soil. High nitrogen levels produce lush green growth, but little to no blooms. Phosphorus is responsible for the flowering and fruiting in most plants.

5. Deer… If you live in an area with deer, their feeding may prevent your hydrangeas from blooming. One solution is to construct a 6 foot (or higher) fence around your garden.