Yes I agree it can be quite invasive, but if you are growing it where it can't reach the lawn area it is quite beautiful as well. It spreads by roots, so if there is a barrier that will work. Or as I am doing, growing it on a hilltop and keeping it in check works as well. When it starts to grow where I don't want it, I dig up that part making sure to get all the roots, and move it where it is more desirable.