Lanceleaf loosestrife was used by the Cherokee as a gastrointestinal, gynecologocal, kidney and urinary medicine, and by the Iroquois as an emetic. I wouldn't want to have any of those needs and be dependent on this as a remedy!
This is one of the identifications that I keep revisiting. The plants were considerably more robust than I was used to. But the keys keep leading me back here. There is a second species, L. hybrida, that is much like this. As far as I know I have not seen that one.