When should I prune my hydrangeas?

The best time to prune hydrangeas depends on what species you have. In the Midwest, lacecap/mophead hydrangeas (Hydrangea macrophylla) and oakleaf hydrangeas (Hydrangea quercifolia) bloom on "old wood" or the previous year's growth. They should be pruned immediately after flowering, but before the buds for next year's blooms have formed. Panicle hydrangeas (H. paniculata) and smooth hydrangea (H. arborescens) bloom on "new wood" or the current year's growth, and should be pruned in late winter or early spring. Dead branches or shoots may be pruned out at any time. 
 

Blooms on old wood (Previous year's growth) - Prune after flowering

• Bigleaf hydrangea (Hydrangea macrophylla)
  • Example cultivars: BLOOMSTRUCK, BLUE WAVE, 'Glowing Embers', LET'S DANCE Series, 'Tokyo Delight'
     
• Oakleaf hydrangea (Hydrangea quercifolia) 
  • Note: Requires little pruning, if any
  • Example cultivars: 'Alice', 'Pee Wee', JETSTREAM, 'Ruby Slippers', SNOW QUEEN

Blooms on new wood (Current year's growth) - Prune late winter, to early spring

• Smooth hydrangea (Hydrangea arborescens) 
  • Example cultivars: 'Annabelle', 'Grandiflora', INVINCIBELLE Series, INCREDIBALL Series 
     
• Panicle hydrangea (Hydrangea paniculata) 
  • Example cultivars: BOBO, 'Limelight', LITTLE LIME, PINKY-WINKY, QUICK FIRE, ZINFIN DOLL