The monarch butterfly is an icon with enduring strength and tenacity while flying thousands of miles. Sadly, wildfires, land development, and greedy people are killing the Western monarch. When developers flatten fields of milkweed and wildflowers, they should be required to mitigate and reseed but aren’t.
One important thing we must do as a county is ban the sale of tropical milkweed. I’ve seen it in local nurseries. The main peril of tropical milkweed (Asclepias curassavica) is that its year-round growth in warm climates disrupts monarch butterfly migration and promotes the buildup of the fatal OE parasite (Ophryocystis elektroscirrha), leading to sick monarchs that don’t migrate or die, causing population declines. Unlike native milkweeds that die back, tropical milkweed provides continuous breeding grounds, trapping monarchs in a cycle of infection and no migration. Other counties have now banned the sale of tropical milkweed.
San Luis Obispo County needs to do the same. Local nurseries should only sell native milkweed such as narrow leaf.
Ethel “Tink” Landers
Arroyo Grande
This article appears in Dec 18-25, 2025.
Asclepias fascicularis is great, it’s native. But what if someone from Kings County visits SLO and buys asclepias fascicularis and brings it back to Kings County, where it is not native? Straight to jail, of course. Or maybe that is too extreme of a distinction for native plant boundaries.
Monarch numbers at the coastal overwintering groves will continue to decline during the next 10+ years because it’s logistically impossible for conservationists to inventory, monitor and protect even 10% of the 10,000,000’s of milkweed plant stems that exist on wildlands around the West (monarch caterpillars feed exclusively on milkweed plants) .