Attract gorgeous butterflies to your garden! Because milkweed is a host plant for the monarch butterfly throughout the Western U.S. and Canada, you'll observe the life cycle of the monarch (Danaus plexippus) by growing this plant. Butterfly caterpillars feast exclusively on milkweed (Asclepias spp.) foliage as a defense mechanism; the toxins in the plant render them distasteful and even poisonous to predators. Milkweed flowers are also valuable to other pollinators, too, including native bees, honeybees, bumblebees, Sphinx moths, and hummingbirds.