Hello plant lovers,
Not sure but it’s probably a variety of Liatris..

It grows like mad! Full sun,in or outdoors,lots of water. It’s quick to flower; long stamens grow with purple blooms….See last pic: this was once one plant-second time splitting it up.
So big,it was dying (pot bound) so I had no choice but split it in February.Used new earth.
Did the best that I could at the time,only had 4” pots..