Late-Flowering Boneset, a native species, has been added to the USWildflowers database (05/05/2013.) Scientific name is Eupatorium serotinum.  Also known as Late-Flowering Thoroughwort.  Photo below was taken in Walker County, GA on Aug 26, 2012.  Go to the Late-Flowering Boneset detail page for more photos and information.

Late-Flowering Boneset – Eupatorium serotinum