Our favorite dwarf hydrangea paniculata! Very long bloom time
From Proven Winners: Loads of flowers on a tiny plant!

This dwarf panicle hydrangea will turn heads! Bobo® hydrangea is engulfed by large white flowers in summer. The flowers are held upright on strong stems, and continue to grow and lengthen as they bloom. No flopping, unlike some panicle hydrangeas! As blooms age, they turn pink.

It is compact and dwarf in habit, and the flowers cover every inch of the plant right down to the ground. This plant was developed by Johan Van Huylenbroeck, the same breeder that developed Pinky Winky® hydrangea.
Grows to 4-5' tall