There is always confusion around the pruning of hydrangeas because you can actually cut away next year's flowers.

Tim Wood, of Proven Winners, gives this advice in Horticulture magazine.

Prune smooth hydrangea (H. arborescens) and panicle, or Pee Gee, hydrangea (H. paniculata) in late winter or early spring. These species set their flower buds on their new growth.

Prune bigleaf (H. macrophylla), oakleaf (H. quercifolia) and climbing (H. anomala subsp. petiolaris) hydrangeas just after they flower. These species form their flower buds in the summer and fall, or "on the old wood." Therefore pruning them in the winter or spring would remove the buds before they have a chance to bloom, and you'd see no flowers that year.

A very cold winter will sometimes kill bigleaf hydrangea buds—keep that in mind if you pruned them at the right time but still have no flowers.

Pruning, Wood writes, is especially important for young plants, even at the expense of flowers during those first couple of years. Here is his advice for young plants.

If the plant is leggy when you purchased it, shear the plant back hard by 1/3  to 1/2 its original size. Once it puts on an inch or two of growth, pinch the branch tips to remove just the growing tip. This tip controls branching.  Once it is removed the buds below it will turn into two or more stems. Once these new branches grow an inch or two, pinch the tip out again.

You can repeat this throughout the first growing season as you are tending your garden.  Although you may sacrifice one year of bloom, this technique results in a well-branched, full-bodied plant that will have more flowers in subsequent years.

The second season in the ground, repeat the pinching practice (or lightly prune.)

Not sure what kind of hydrangea you have? Consult our photo gallery.