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 — and to plant A. speciosa for Monarch caterpillar 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. While Monarch butterflies are rare in south coastal BC, all Asclepias species are coveted food plants for most butterflies.
Bloom Time: Summer through autumn.