top of page


Butterfly 2 smr.png

Updates for California are provided by two liaisons:  Terry Smith for Northern CA/Bay Area, and Susie Vanderlip for Southern CA,, either one for Central California. Please contact them directly for additional information.


1000% Increase in Overwintering Monarch Population along Central Coast California as of Jan. 2022!


What a difference a year makes. In November 2020, the overwintering count was so low (less than 2,000 across approximately 4000 sites in central coast California) that it was dubbed the ‘collapse of migration’. This past November 2021 the count, verified at the New Year’s count, revealed 250,000 monarchs!
An astounding rebound in just one year.


What was responsible for this amazing rebound is not known! Monarch butterflies are resilient and adaptable, but conservation scientists have done calculations, and 2,000 overwintering monarchs from Nov. 2020 cannot propagate sufficiently to product 250,000 monarchs in Nov. 2021. Was it the large increase in winter propagation in the Bay Area and southern California, referred to as resident monarchs this past year? Are there monarch populations in areas across the western states no one is aware of? These question and more are on the minds of conservation scientists as more and more research is being done to understand where and when monarchs are breeding and migrating in California.


Monarch butterflies that breed in North America west of the Rocky Mountains are known as western monarchs. In the late fall, most western monarchs have migrated to the California coast and spent the winter (late November to February) clustering in groves of pine, cypress, and eucalyptus trees, during which time they do not breed (reproductive diapause). As temperatures warm and daylight hours increase in February, they mate and migrate inland to lay eggs on emerging milkweeds.


Historical Migration Perspective:

According to Xerces, 4.5 million monarchs overwintered on the California coast in the 1980’s. By 1997, there were 1.2 million monarchs. As of 2015, that number had declined to 293,000; in 2019, the decline fell to 30,000 and, in 2020, less than 2,000. This was alarming to monarch conservationists and urban gardeners alike.

In November 2020, there were also a significant number of monarchs found inland and in southern California that bred throughout the winter sustained by non-native tropical and balloon milkweed. That year there was a large “urban” or resident population. Reports of dozens of eggs being laid on mostly non-native milkweed all winter led to reports of hundreds of monarchs eclosing (emerging) from chrysalides January thru March 2021. Now, in 2022, we are happy to report the unprecedented increase to 250,000 overwintering monarchs. What population spread occurs from this population to all areas of California as well as other western states is eagerly awaited.

What can Californians do to help?

Many Californians and conservation groups are asking, what can individuals do to help the monarch population sustain and grow to increase the recovery of the population of western monarchs, as 250,000 is still much lower than needed for long-term sustainability. Most critical is for as much monarch butterfly habitat be planted as possible and overwintering sites restored and developed. Native milkweed is the recommended by Xerces and California Department of Fish and Wildlife (CDFW) along with nectar plants. Non-native milkweed, especially tropical milkweed Asclepias curassavica, is still quite available and used by resident monarchs as well as overwintering monarchs that disperse to feed and breed in February, before native milkweeds have come back from dormancy. There is still controversy over the pros and cons of tropical milkweed with conservation scientists both pro and con.


On a positive note, March thru October of 2021 found a great deal more native milkweed available through growers and nurseries throughout California. Other organizations, such as Monarch Watch and Xerces, provided plugs of native milkweed free to 1 acre or larger habitat restorations as well as for purchase at smaller quantities. In addition, Regional Conservation Districts, funded by the State of California developed restoration projects for overwintering sites and began research on  early growth native milkweeds that might be available in February when overwintering monarchs disperse to feed and breed. Many non-profits and local monarch enthusiast also initiated planting many small new butterfly gardens across California and provided more educational programs for the public. As a result, the April thru October 2021 monarch propagation in California was substantial.

Another significant change in 2021 was the effort by conservation groups, Facebook groups, blogs, and websites to educate the public about the California Department of Fish and Wildlife Ruling that declared ‘no touching and no rearing’ of monarchs allowed in California. The reason for the Ruling is to allow Nature to proceed untampered with by humans. This is standard in conservation efforts. With monarchs, it intended to eliminate urban gardeners from protecting caterpillars and chrysalids; no putting them into habitats or raising eggs, caterpillars or chrysalids inside; and no mass rearing. This was, of course, a major change for many urban gardeners who have long felt compelled to save every egg and caterpillar possible. However, in conservation science, this activity promotes saving weak or even sick caterpillars, and weakens the overall population.

Pesticides and Herbicides:

Of on-going critical importance for the survival of California monarchs as well as all pollinators is the reduction of pesticides and herbicides across all ecosystems. Gardeners are encouraged to eliminate pesticide use. Many monarch caterpillars are killed or weakened by ingesting plants that have been grown with pesticides or in gardens where they’re used. Neonicotinoids used by growers to bring plants to large retail stores are serious killers of pollinators from bees to butterflies. (Pesticides | The Monarch Joint Venture). The weed killing herbicide glyphosate (key ingredient in RoundUp and other herbicides) is another known toxin for milkweeds. Please participate in responsible pesticide use in our environment. Learn more from Pesticide Action Network (PAN) Pesticide Info | California Pesticide Use


Stay tuned for updates and recommendations for monarch butterfly gardeners and habitat creation across California. For more information on California monarchs by region, see below.


Northern California | Bay Area & Surrounding


Northern California Monarchs, particularly those in the greater Bay Area, have continued to fluctuate in numbers and behaviors.  Numbers at the northern overwintering sites have remained low in recent years, but there is evidence of a growing year-round population - particularly in temperate areas along the coast.  Inland areas have seen very few Monarchs in recent years, but with the larger numbers seen at the other overwintering sites in the winter of 21-22, hopes are high that there will be many more sightings across the state in 2022. With changing conditions, observation and data gathering has become increasingly important.  Several community science projects provide opportunities for individuals to contribute to these efforts.  For more information on how to participate in link here.

Monarch habitat has been established in a large number of both home and public gardens in Northern California, and several projects are currently underway.  Xerces, Monarch Joint Venture and RCD’s in the area are working to establish habitat on farmland and work is also being done restoring some traditional overwintering sites.  At last count 13 mayors have signed on to the World Wildlife Fund Mayors’ Monarch Pledge and more are considering it.   For more information and details of projects throughout Northern California link here.


For further information please contact:

Central California

The Fall 2020-Winter 2021 “migration” was unusual and disturbing to all as

few surviving Western monarchs seemed overwintered either on the coast, or inland. Only 1,642 were counted by observers along the California coast at the 2021 New Year’s Count However, as the California Introduction states, the 2021 Thanksgiving/2022 New Year’s Counts revealed a stunning 1000% increase in overwintering monarchs, rising to 250,000. In Monterey County, the city of Pacific Grove celebrated the return of approximately 14,000 monarchs to their sanctuary, and there were thousands at other sites in Big Sur. San Luis Obispo County had over 90,000 butterflies reported at its overwintering sites, including the California State Parks-managed Pismo Beach Butterfly Sanctuary which had the second highest count at an overwintering site this season at 20,871 butterflies​.


Overwintering behavior. With high temperatures increasing into the 80’s by early February 2021, extensive mating behavior was observed and monarchs expected to disperse early./

Gravid females ovipositing on new milkweed shoots in January and February was also seen in 2021. Even when there was no active milkweed in the garden, male monarchs patrolled regularly apparently searching for females.

A major improvement to the native milkweed availability would be to extend the growing season for natives, now dying back early in the late summer/fall due to drought and removal of watersheds, by reintroducing beavers to revive riverscapes & extend watersheds. See Reviving Riverscapes, Science News March 27, 2021.

In Carmel Valley, Scott Hennessy has been raising a form of Asclepias fascicularis that breaks ground earlier than the standard form, stays greener well into Fall, apparently responding extremely well to occasional watering, and has broader leaves.

2 Favorite Monarch nectar plants for home gardens covering all seasons. 

Photo 1.jpg
Photo 2.jpg

Monarch nectaring on yellow evergreen Mexican Sunflower bush, Tithonia diversifolia, Blooms July to April in Central and S. California.

Southern California

2021 was a productive year for monarchs in southern California
which covers eight counties and a wide variety of microclimates. Resident monarchs bred across the southland from January thru March. April thru August 2021 was the most abundant season for monarch breeding in urban gardens as reported in posts on the Facebook Group Monarch Butterfly Guardians – southern California. By mid-July thru September tachinid flies killed up to 99% of caterpillars and/or chrysalids in many areas. Urban gardeners were prohibited from touching or rearing monarchs by California the Dept of Fish and Wildlife (CDFW) Ruling which eliminated using habitats or rearing in the house, which increased the predation of caterpillars and chrysalids. San Bernardino County reported breeding until high summer temperatures reached over 100 degrees in July after which monarchs were then no longer present.

In September 2021, a reduction of monarchs and breeding of 80% to 100% was reported across the southland. It is not known why this happened. It is also not known if southern California fall monarchs migrated to central coast overwintering sites in the fall.

Because there is much unknown about southern California monarch breeding and migration, southern California urban gardeners are encouraged to get trained and report on the Monarch Larva Monitoring Project (MLMP)

to help us all understand the movement and breeding in the southland:

In addition, if you are interested in southern California monarch activity, you are encouraged to join the Facebook group: Monarch Butterfly Guardians - southern California

Events and Projects Across the Southland


Many new monarch habitat planting projects were initiated in 2021 by city agencies, parks, schools, associations, businesses, and individuals. The number of urban gardeners planting monarch habitat expanded as many people became interested in helping save monarch butterflies. CDFW, Xerces, and Monarch Joint Venture actively urged planting native milkweed which spurred nurseries and growers to make more native milkweed available to consumers. Narrowleaf milkweed was most available. Rogers Gardens home and garden center offered a milkweed exchange program whereby customers could exchange a tropical milkweed plant from home and receive a free native narrowleaf milkweed.

  • Resource Conservation District of Greater San Diego County

  • Ventura Resource Conservation District

  • Sepulveda Basin Wildlife Preserve

  • Front Porch Retirement Communities

  • City of West Hollywood

  • Girl Scouts of Orange County

  • Laguna Woods Village for 55+

  • California Associations Institute (CAI)

  • Discovery Network and Toyota Motors of North America

More details on these and future projects at Monarch Projects Across the Southland
Please email and share about Monarch Butterfly habitat projects in southern at

Informative Resources

Photo 3.jpg
Photo 4.jpg
CA 20210707_122423E2 sm.jpg

Help Us Conserve the

Western Monarch

WMA Logo White Silhouette with shadow sm
bottom of page