If the old stems are typically dead and do not leaf out, you can cut them all the way down.

If stems always leaf out (normal), you can cut the petiole string that connects the bloom to the stems. Any stems that (odd) have not leaf out by the end of May can also be cut all the way down.

Old blooms can always be disposed by cutting the petiole string that connects the bloom to the stem.

Thank you Luis!! Most appreciated.

Most hydrangeas don’t need to be pruned to the ground unless stems are winter killed. Panicled hydrangeas do tolerate hard pruning down to a foot or two, but they are just fine if all you do is snip off the old blooms and let everything just grow. I don’t prune mine; I just deadhead.

Thanks - good advice. My first experience with these hydrangeas.