The Western Monarch Butterfly

Often, when we think of monarch butterflies, the eastern monarch butterfly comes to the mind with its spring arrival in the United States and its iconic fall migration to the mountains of Mexico to overwinter. In California, we are fortunate to host the western monarch butterfly.

2016 Bolinas, CA Overwintering cluster of Western Monarch Butterflies. Photograph by Stephan Meyer

2016 Bolinas, CA Overwintering cluster of Western Monarch Butterflies. Photograph by Stephan Meyer

The western monarch (Danaus plexippus) spends its spring and summer west of the Rocky Mountain ranges. In the fall it migrates to the California coastline (from Mendocino to Baja), where it seeks moderate temperatures and protection from storms by clustering in tree groves. The arrival of the mariposa (monarch butterfly) along the coast signals a cultural beginning to autumn. The butterflies also symbolize change, transformation, rebirth, hope, and abundance.

The 2024 Xerces Society mid-season count recorded just 272 monarchs in Marin County — a staggering 92% decline from the 3,421 counted in 2023. This alarming drop reflects a broader statewide trend, with California witnessing a 96% overall decrease in observed monarchs from 2023 to 2024. Download Xerces Data. Threats to monarchs include loss of breeding and overwintering habitat, exposure to insecticides, and the effects of climate change.

In response to declining numbers, the U.S. Fish and Wildlife Service (USFWS) proposed listing the monarch as a threatened species under the Endangered Species Act (ESA) in December 2024. The public comment period closed in May. Public input is now under review and the USFWS is expected to issue a final decision by December 2025.

EAC is committed to supporting thriving monarch populations in Marin and was a co-founder and fiscal sponsor of the Marin Monarch Working Group. Through advocacy, habitat protection, community science, and education, we work to safeguard the western monarch’s habitat and migratory pathways.

Read on to learn how you can take action to help protect monarchs in Marin!

How You Can Act Locally to Help the Monarch

“Today’s remaining monarchs are calling us to get real. To not merely know things and feel things about them but to do things for them. To become attuned to what they need where and when, to think about the plants in our gardens and parks, about how we manage weeds, about where we place development. They are asking us to do for their lives as we do for our own.“ - Mary Ellen Hannibal (quoted from Marin Monarch Movement report introduction)

Monarch on Narrowleaf Milkweed (Ascllepias fascicularis)

Monarch on California goldenrod (Solidago californica)

Monarchs sunbathing while overwintering in central California

Habitat loss, pesticide use, and climate change are the chief driving forces behind monarch population decline. Fortunately, we can take actions to help monarchs in our own backyards!

  • Plant native milkweed

    • Why: monarch caterpillars feed exclusively on milkweed

    • When: plant in early spring

    • Where: in areas at least 5 miles inland from the coast

    • Which species: Focus on native varieties like Narrowleaf Milkweed (Asclepias fascicularis) and Showy Milkweed (Asclepias speciosa). Do NOT plant tropical milkweed (A. curassavica) as it encourages monarchs to overwinter and disrupts their migration patterns.

  • Provide nectar-rich plants

    • Why: adult monarchs rely on nectar-rich flowers for sugars and other nutrients

    • When: early spring, late-fall and winter-blooming nectar plants are best as they are critical for fueling monarchs during migration

    • Where: all locations, including coastal locations

    • Which species: California fuchsia, goldenrod, monkeyflower and buckwheat are a few examples. Find a seasonal planting list here.

  • Join community science and monitoring

  • Get involved in local restoration events

RIGHT ACTIONS IN THE RIGHT PLACE

In Marin County, this means we need to develop a coordinated response, enlisting residents, nonprofits, commercial businesses, agriculture, schools, golf courses, local governments, and others in a variety of actions to prevent a total population collapse of this iconic species.Specifically, we need to plan our actions based on habitat needs in the coastal and inland areas if we want to support the population effectively.• Inland areas should provide breeding and migratory habitat support with lots of native milkweed, nectar plants, and fresh water.• Coastal areas should provide and protect rich and dynamic overwintering tree covers, fresh water, and native nectar plants.• Coastal areas must be free of milkweed.

• Inland areas should provide breeding and migratory habitat
support with lots of native milkweed, nectar plants, and fresh
water.

• Coastal areas should provide and protect rich and dynamic
overwintering tree covers, fresh water, and native nectar plants.

• Coastal areas must be free of milkweed.

Thank you to the individuals and organizations who contributed information, content, designs, and photographs to bring this vision to life

  • Organizations:

    Xerces Society, Salmon Protection and Watershed Network (SPAWN), Marin Audubon Society, Home Ground Habitats, and the California Native Plant Society Marin Chapter.

  • Individuals:

    Mia Monroe, Mairi Pileggi, Mary Ellen Hannibal, Jessica Taylor, Karen Campbell, Audrey Barth, Grace Milstein, Carolina Auerbach, Audrey Fusco, Ed Nute, Max Sarosi, Alice Cason, Marcia Basalla, Sarah Killingsworth, and Carlos Porrata.

  • Financial Supporters:
    Thank you to the individuals who financially supported this project. Your contributions made this work possible.
    Cynthia Lloyd, Mia Monroe and Stephan Meyer, Karen Culler and Thomas Weidinger, Claire John Eschelbach, Gail Grasso The Nancy P. and Richard K. Robbins Family Foundation, and David and Patty Wimpfheimer.

Recommended Retail Nurseries

Marin County Nurseries

 

CNL Nursery:
254 Shoreline Hwy Mill Valley, CA 94941
(415) 888-8471 | cnlnatives.com

Green Jeans:
690 Redwood Hwy Mill Valley, CA 94941
(415) 389-8333 | greenjeansgardensupply.com

 

Mostly Natives:
54 B St., Unit D Point Reyes Station, CA 94956 (415) 663-8835 | mostlynatives.com

O'Donnells Fairfax Nursery: 1700 Sir Francis Drake Blvd, Fairfax, CA 94930 (415) 453-0372 | odonnellsnursery.com

 

Nurseries Outside of Marin County

 

Curious Flora Nursery:
740 Market Avenue Richmond, CA 94801
(510) 215-3301 | curiousflora.com

Cal Flora Nursery:
2990 Somers Street Fulton, CA 95439
(707) 528-8813 | calfloranursery.com

The Watershed Nursery:
601 Canal Blvd Richmond, CA 94804
(510) 234-2222 | watershednursery.com

 

Emerisa Gardens:
555 Irwin Avenue Santa Rosa, CA 95401
(707) 525-9644 | emerisa.com

Oaktown Native Plant Nursery:
702 Channing Way Berkeley, CA
510-387-9744 | oaktownnursery.com

 

Recommended Wholesale Nurseries

 

Hedgerow Farms:
21905 County Road 88 Winters, CA 95694 (530)-662-6847 | hedgerowfarms.com

Home Ground Habitats:
PO Box 592, Novato, CA 94948
(415)-299-9244 | homegroundhabitats.org

 

Larner Seeds:
235 Grove Road Bolinas, CA 94924
(415)-868-9407 | larnerseeds.com

SPAWN Nursery:
9255 Sir Francis Drake Blvd., Olema, CA 94950
(415) 663-8590 | audrey@seaturtles.org seaturtles.org/campaigns/native-plant-nursery

 

Is your favorite California native plant nursery missing?
We may not know about them yet. Email us to add them to our online listings.
If they are carrying non-native milkweed (like tropical milkweed) or other harmful non-native plants, they were not included on this list. Kindly ask them to remove harmful species from their inventories to protect western monarch butterflies.
Then we can update our list to include them.

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