Grow California native plants that attract pollinators with their nectar. You can find a great list of pollinator-friendly native nectar plants online at Xerces.org.
Grow plants that Monarch butterflies use to lay their eggs and caterpillars will eat - like native milkweed! To learn more about growing California native milkweeds, visit Xerces.org.
Only use native milkweeds and avoid non-native and tropical milkweed plants as they can harm Monarch butterflies and their larvae. You can find milkweed and other host and nectar providing plants for Monarch and other butterflies that are local to your area by using the advanced search on www.calscape.org and in this terrific article from our friends at the Theodore Payne Foundation: