Is it ok to cut / trim back in first of October, when the white blooms turn to dark?

HI Bill Thanks for asking! Panicle hydrangeas can be deadheaded at any time to remove the dark blooms. Pruning can be done in late fall, once the plant has gone completely dormant (i.e., has lost all of its leaves and has been bare for at least two weeks), or in early spring, just as the new growth begins to emerge. Aim to cut the plant back by about one-third its total height. As always, please feel free to reach out to us at any time with any plant questions or concerns. Email us at helpdesk@provenwinnersdirect.com. We are happy to help! Cori at Proven Winners Direct