The Need for Milkweed

The Need for Milkweed

In the 1980s, monarch butterflies filled trees from Marin County to San Diego County during their migration season. This year, the Xerces Society reported only 1,914 monarch butterflies overwintering (the process by which organisms pass through or wait out the winter season) on the California coast. This is a 99.9% percent fall from the 1980s, a truly shocking statistic. Following two years of less than 30,000 butterflies, it appears that the western monarch butterfly migration is nearing its demise. 

For decades, the monarch population in the West has suffered most from the loss of their habitat, specifically the destruction of their California overwintering sites and loss of both milkweed for caterpillars and fuel migration resources from its flowers. They’re also heavily impacted by climate change and pesticides. Despite these incredibly sobering statistics, it is important to remember that now is a critical time to try and help their population as much as possible. One way to do this is by visiting the Monarch Joint Venture’s Monarch Conservation Plan for ideas on how to conserve the monarch butterfly migration. 

Another way to do this is by planting milkweed. Milkweed is both a food source and the sole host plant for monarch eggs that are laid on the underside of the leaves. There are over 100 native species of this wildflower (not a weed, as its name implies) in the U.S. and Canada, and they are characterized by the sticky white sap that oozes from their damaged leaves.  

Milkweed contains various levels of cardiac glycoside, which is a compound that renders the plant toxic to most insects and animals. Monarchs and caterpillars use these compounds as a defense, storing them inside their tissues to render them inedible or toxic to birds looking for a quick snack. Not only does the close relationship between the monarch and the milkweed represent a coveted food source and host plant, but it's a life saving defense as well. 

To plant milkweed at home, you can choose between three good all-around choices for gardens in most regions of the country: Common Milkweed (A. syriaca), Swamp Milkweed (A. incarnata), and Butterfly weed (A. Tuberosa). Note: Tropical milkweed (A. curassavica) is a non-native species that should be avoided as it can cause harm to monarchs. Leading monarch butterfly conservation/restoration efforts recommend planting regionally native milkweeds whenever possible. Click here for information on Native California Milkweeds. You can also click here for information about roadside milkweed that grows in California. 

While the monarch butterfly situation looks rightfully dire, there still is hope. Despite denying listing the species under the U.S. Endangered Species Act (ESA) in 2014, the U.S. Fish and Wildlife Service announced in December 2020 that listing the monarch butterfly under the aforementioned act was “warranted but precluded by higher priority actions.” With this decision, the USFWS agreed that monarchs were (and still are) being threatened with extinction, and the warranted but precluded determination makes it a “candidate” species, a status that comes with near term positive benefits. As a candidate species, monarch butterflies may be included in project planning and review on lands managed by deferral agencies. Additionally, this may also lead to more funding for monarch conservation from public and private entities. 

With the current decision, the status of the monarchs will be reevaluated annually. At present, the species currently remains unprotected because of a rule regarding the entire species/subspecies of invertebrates needing to be classified as endangered as opposed to the way species, subspecies or “distinct population segment” of vertebrates are classified accordingly and protected under the ESA. Nonetheless, efforts from organizations such as and Xerces Society are working to advocate for monarch butterflies in the meantime

E-mail me when people leave their comments –

You need to be a member of SCOCO Network to add comments!

Join SCOCO Network


  • I have been growing the Narrow-leafed milkweed in my garden for about 4 years. Every year it spreads more, and I conserve the wonderful seeds to scatter and spread. With what might be the last of our rains, perhaps now is a good time to scatter! However, I have yet to see one monarch butterfly or caterpillar settle on this host plant out here in Livermore. It could be that we are not on the migration pathway. When I went to Pacific Grove in February, I was heartbroken to learn that very few (if any?) monarchs had returned to their sanctuary there this winter. I walked the paths, everything was empty. It could be that it was too late in the season, I just hope it is not too late for the species! Has anyone seen the Monarchs? If so, where?
This reply was deleted.