I believe this plant is a biennial. When first seen, I thought I was seeing baby moss verbena, but as the plant had an upright habit, I discarded that tenative id.
Growing in the middle GA sandhills, I posted it at the walter reeves site
for id, but no one had any idea.
First pic is after the blooms have finished, second is a clump in full glory, third is a close-up with macro, shot back in October.
This plant has a short bloom period, like a week or two.