I have monarda in my "cutting garden" and cut them as soon as they bloom. They keep on reblooming until frost. Those that I don't cut are often a little more sluggish, as they're expending energy on seed production. Then I don't cut it to the ground until a hard frost has killed it. (But by then I'm normally so depressed that winter's coming, that I often don't go out to that garden until spring). It's one of those tough-as-nails plants that can take almost anything, except for powdery mildew.