This lifeform is found east of the Continental Divide in North America.

Green comet milkweed (Asclepias viridiflora) is found from southern New England west to Ontario (Canada) and south into Florida and Texas. This milkweed is also found in the plains and southwestern Texas. Note the long narrow flower with the petals close against the flower stem and the wavy edge of the leaves.

Asclepias (Milkweeds) is a genus of about 108 species native to the New World and  South Africa.  This genus has  recently become established in Eurasia.  The Britton and Brown  three-volume botany on the eastern United States (An Illustrated Flora of the Northern United States and Canada, 1913) shows 21 species.  Kartesz shows 79 species and 15 subspecies in greater North America, including the United States, Hawaii, Canada, Greenland, Puerto Rico and the U.S. Virgin Islands.  The typical milkweed grows its seeds in pods that open in fall or winter releasing the seeds to the wind.  The well-known monarch butterfly  (Danaus plexippus) appears to feed primarily on this genus.