Hm, so it seems like that milkweed does have a distribution in California, but is not one of the native ones. https://www.calflora.org/app/taxon?crn=9705 https:

Hm, so it seems like that milkweed does have a distribution in California, but is not one of the native ones. https://www.calflora.org/app/taxon?crn=9705 https://www.calflora.org/app/taxon?crn=9705 says it's not native, and Calscape doesn't list it at all. If you're in California, I'd highly recommend getting the narrow-leaf instead, if you don't mind spending a little more money. Also, if you can, plant some native Salvia nearby for them to pupate on. Salvia Clevandii does quite well. They'll also pupate on arbors, trellises, fences, etc.