We are on sandy loam soil along the Mississippi in Iowa. Seems to grow in conjunction with small white clover patches about 3' diameter. Not a take-over plant. Most of the petals that surround the blossom have fell off. I like it and will mow around it. Have never seen it before in other places in the region I've lived. Sorry to leave this as a comment. Couldn't get to the description page once I put the photos on. Thanks for looking.
Prunella vulgaris (non-native)
Thank you very much. I'll read about those.