Antelope-Horn Milkweed, a native species, has been added to the USWildflowers database (5/13/2014.)  Scientific name is Asclepias viridis. Photo below was taken in a Chickamauga Battlefield, Catoosa County, Ga on May 12, 2014. Go to the Antelope-Horn Milkweed detail page for more photos and information.

Antelope-Horn Milkweed – Asclepias viridis