I whacked them to within 6" from ground and they came back bigger and better in Houston area. Despite the whacking, they were unruly by season's end. I yanked them out and put a clump in a container, which I then sank in the ground, that way I only have to worry about one unruly clump. So far, so good.

I think you could whack them down and they'd come right back like bossyvossy's did. I don't even know if it is possible to kill a 'Henry Duelberg' salvia on purpose. You know its history? Greg Grant found it on a Mr. Henry Duelberg's grave in an unirrigated cemetary somewhere in rural Central TX. So, anything that can survive in Texas in an unirrigated cemetary probably is really tough and likely can handle anything you throw at it.

Thanks, both of you! Yes, Dawn, I looked it up prior to purchase. I loved the story! There's also a white one named after Henry's wife, Augusta.