Asclepias is a genus of plants commonly known as milkweed. When broken, the stems or leaves of milkweed issue a milky sap that defends the plants from being eaten. Another common factor amongst the milkweeds is the unusually generous nectar that their flowers provide to pollinators. This makes them extremely attractive to domestic and wild bees, and an important food crop for adult butterflies, including the endangered Monarch butterfly.
To add confusion, a couple of milkweed species were, until recently, listed as noxious weeds, so the availability of their seeds was very limited. In a (sensible, we think) effort to conserve the Monarch's feeding habitat, these plants have been de-listed. Campaigns are underway to plant Asclepias enthusiastically for pollinator conservation.
The Monarch butterflies that have received the most attention in the last couple of years migrate between central Mexico and southern Canada east of the Rocky Mountains (largely into Ontario and Quebec). A western population migrates between south coastal California and the BC interior. There is limited, but occasional crossover between populations. All Asclepias species are coveted food plants for most butterflies.
