My experience is that it spreads quite slowly. The size of the leaves are larger in the subsequent years but spread is minimal. Mine are in deep shade though so maybe if it has more sun it spreads more? I dunno.

Barb
southern Ontario, CANADA

The ones that I have now are planted in a spot where they get morning sun, afternoon shade. I've had them in the past and have never experienced any problem with them being invasive. They are nice and very slow to spread. They are always the first to bloom every year.