Answer: Your blue and pink flowering hydrangeas are probably Hydrangea macrophylla or big leaf hydrangeas. These plants develop flowers on new growth on old wood. To prune big leaf hydrangeas, prune all wood down to about knee high in the spring, just as new buds begin to swell on the stems. This will provide plenty of old wood on which new flowering stems can develop. The white flowering hydrangea can be Hydrangea arborescens (Annabelle) or Hydrangea paniculata (Pee Gee), or Hydrangea quercifolia (oakleaf). Theres also the Endless Summer (H. macrophylla) that is white flowering. Until we know for sure, I can't suggest when or how to prune. Try to determine its true identity and we'll be happy to supply pruning guidelines.
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