Thanks for all the comments, folks! (Been out of town for 4 days and am trying to catch up.)
THGA - I haven't had this very long so I can't tell if it's invasive, though I wouldn't mind if it is! I saw some bog sage at a plant sale recently and it's a little different. Also, I've been told that bog sage needs moist soil and this one's doing well in a sandy area.
Judy - It's good to know that it can get tall. I'll have to follow Calalily's advice and cut it back to prevent legginess (is that a word??)