I have these purple flowers in a shaded corner of my yard, along with my hostas and some other stuff I really haven't weeded all summer. Is this thing a weed or what? Its kinda pretty, but it has prickly stems almost like a nettle plant. It really doesn't sting, but it just doesn't feel like any flower I ever saw. I never planted them, so I'm thinking its some kind of weed... anyone know what the heck it is?? I am in Wisconsin, where nothing lives in the winter... Thanks so much. terri