Charleston, SC suburb yard, part shade, low growing. near woods
Hi TL,
this plant is Mazus japonicus, but the identification is somewhat confused because it is sometimes called Mazus pumilus or Mazus reptans. It is not native and appears to be spreading, but is somewhat showy. You can see more pictures here: http://www.missouriplants.com/Blueopp/Mazus_japonicus_page.html
Sincerely,
Steve Hill, Ph.D., Botanist, SCNPS