United States
USDA Plants National Database recognizes two subspecies of A. asperula, both native to the U.S. Subspecies capriconu is native to many of the Great Plains states and parts of the Southwest. Subspecies asperula is native to most of the western part of the U.S., including Colorado. They vary in the shape of their leaves, the color of their hoods and the length of their peduncles.
This is an Important larval and adult food host for many of our native invertebrates, the most popular being the Monarch butterfly (Danaus plexippus). Generally, Monarch butterflies will lay eggs on any Asclepias species and preferences change depending on season, habitat, and health of the milkweed. Provide a wide selection of milkweed species in your garden for these butterflies.