Thanks for writing. It depends on what type of hydrangea you have; most of the common blue and pink varieties tend to bloom in early summer (as do oakleaf types). The sun-loving paniculata types (like 'Limelight') tend to bloom in mid- and late summer.
If you just planted your hydrangea this year, it may have put energy into getting established instead of blooming. If this is the case, it will probably bloom just fine next year if you don't prune it and if it has good growing conditions for its type. Learn more:
---Justin, Senior Garden Editor, BHG.com