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Southern California provides important habitat and overwintering sites for western monarch butterfly populations, which have declined by 95% since the 1980's. This is in part because milkweed, the plant upon which all monarchs depend during the early stages of their lifecycle, is also declining.
In response, a great number of very well-meaning people throughout San Diego County and beyond began growing tropical milkweed. This nonnative species of milkweed was readily available at nurseries, had showy flowers, remained green year-round and very successfully attracted monarch butterflies. Many gardeners were thrilled to have a plant that attracted monarchs to their yard all year round. But at what cost?
It was quickly discovered that planting tropical milkweed was not the panacea it seemed. Indeed, we understand now that planting this nonnative species of milkweed is actually detrimental to the recovery of western monarch butterfly populations.
This is because:
Native milkweed species are in short supply in San Diego County. This is true not only for home gardeners, but for conservation practitioners working to restore native landscapes. In response, Earth Discovery Institute has partnered with the Pollinator Alliance of San Diego, U.S. Fish & Wildlife Service, Resource Conservation District of Greater San Diego, and Endangered Habitats Conservancy to develop a seed bank of native milkweed in San Diego County. In 2020, we successfully grew native narrowleaf milkweed (Asclepias fascicularis) from seed at our milkweed farm in east county. In 2021, we are tripling the size of our milkweed farm and in addition to growing narrowleaf milkweed (Asclepias fascicularis), we are now growing native woollypod milkweed (Asclepias eriocarpa). We are already making plants available for restoration projects across the county, and to home gardeners during our annual plant sale in the fall.
Learn about native narrowleaf milkweed in San Diego County:
Additional resources and reading: