Whorled Rosinweed, a native species, has been added to the USWildflowers database (08/06/2012.) Scientific name is Silphium trifoliatum.  Photo below was taken in Wilson County, TN on Aug 4, 2012.   It  is also known by the common name Three-leaved Rosinweed.  Go to the Whorled Rosinweed detail page for more photos and information.

Whorled Rosinweed, Three-leaved Rosinweed – Silphium trifoliatum