Fly Poison, a native species, has been added to the USWildflowers database (09/05/2011.) Scientific name is Ambrosia artemisiifolia.  It is also known by the common names Annual Ragweed, Small Ragweed, and Roman Wormwood.  Photo below was taken in Walker County, Georgia on Sep 4, 2011.   Go to the Common Ragweed Detail Page for more photos and information.

Common Ragweed, Annual Ragweed, Small Ragweed, Roman Wormwood - Ambrosia artemisiifolia