That's a good question. I love my Bee Balm but it is widening every year. If there are rhizomes down there, when it gets too big, take you shovel, cut off half and plant it someplace else (or gift it to a friend). My daughter started one from a broken stem on mine. I didn't know you could start them from cuttings but she did - I think just to prove her mother wrong.
By the way, your's is really pretty and full. Mine is a little sparse this year - our usual summer rains have not happened.
