What is this plant called

It seems to be invasive and looks a bit like bee balm or at least like my plant that I bought as bee balm, but that one has never flowered.
Anyone know for sure what I have here?
This is the plant. It is about 3 times this width now.
close up of the flowers. The bees love it.
  3 answers
  • Ellen H Ellen H on Oct 06, 2013
    It is eupatorium coelestinum, also known as hardy ageratum, or blue mistflower. It blooms in late summer/early fall. Could be considered invasive unless you love it (I do) - the roots are quite shallow, making it very easy to pull out if it comes up where you don't want it. Mine grows quite tall - did you pinch yours back?
  • Someone else was asking about this plant not too long ago. I quite like it but we don't grow it here.
  • Doreen Nestell Doreen Nestell on Oct 08, 2013
    Ellen H. Has nailed this one.