Cankerweed, a native species, has been added to the USWildflowers database (11/20/2012.) Scientific name is Prenanthes serpentaria.  It  is also known by the common names Lion’s Foot, Snakeweed, Earthgall, and Butterweed.  Photo below was taken along the Blue Ridge Parkway, Haywood County, NC, on Aug 1, 2011.   Go to the Cankerweed detail page for more photos and information.

Cankerweed, Lion’s Foot, Snakeweed, Earthgall, Butterweed – Prenanthes serpentaria