Hi Rae,
Something tells me you have some experience with mountain mint being invasive.
I'm not sure where you are but location but that can make a difference, and different species can act differently. Maybe you are north? But then, Hoary Mountain Mint (Pycnanthemum incanum) is on the endangered list in Vermont, New Hampshire and Canada and that's pretty far north. I'm wondering because I've not heard of P. incanum being invasive. But, I'm not sure about other species of Pycnanthemums.
