I found this flower along our driveway. The soil here is very sandy. It was amongst a patch that contains fleabane and other weed types. The plant is approx. 2 ft tall. The flowers are at the top part of the plant at this time they are only on the top sets of flowers. The flowers themselves appear to be a light purplish color.
your plant is an introduced plant from further south called Stachys floridana, the Florida hedgenettle. It has white tubers and is often spread in garden soil from place to place. Some consider it to be a weed in the Carolinas. It does have a nice flower. You can find out more about it here: http://plants.usda.gov/java/profile?symbol=stfl4
Thanks for asking!
Steve Hill [Ph.D.] SCNPS