|I have a woody salvia that has deep blue petals and a|
You can cut it back as far as you like. If it has new growth on it then cut that off to make cuttings as you mentioned. If no new growth has appeared yet, wait until it does. I suggest not cutting the overall plant back more than to about 4-6 inches high right after you transplant it. It should resprout in a few weeks.
Thanks for the question. Please stop in again soon!