Answer: The bigleafed hydrangeas bloom on old wood that grew the year before, so the best time to prune is immediately after it blooms. At that time you would remove some of the longest branches by cutting them off low down by the ground. You would also head back some of the remaining branches. If you prune it back hard in the spring, you may see fewer (or no) blooms this coming summer. Spring pruning should be limited to removal of winter damaged, dead or diseased branches. I hope this helps.
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