How planting California natives helps bring back monarch butterflies, and other pollinators

Vilma Aquino still remembers when monarch butterflies flocked to Mare Island. This peninsula, which is part of Vallejo in Solano County, used to be a hotspot for monarchs looking to settle down during the winter months. 

“When I would drive into Mare Island, way back when, there would be hundreds of butterflies,” Aquino said. “I thought I'd died and gone to heaven.”

But much has changed since Aquino moved to the area in 2007. Monarch populations throughout California have seen a steep decline for decades. Researchers say this is likely related to habitat loss, climate change and other impacts on the state’s ecosystems. Vallejo locals note these butterflies have nearly disappeared from Chapel Park, an area on Mare Island where they once gathered in the thousands and is now the last semi-active overwintering site for monarchs in Solano County. 

As a co-founder of the volunteer-run Vallejo People’s Garden, Aquino said she has encouraged residents to plant native species that could help attract monarchs — and other pollinators — back to Mare Island.

“As we do these projects, community members are walking through and seeing it and wanting to know what's going on,” she said. “Our hope is that we can spark inspiration for others … so that this whole island can be populated with Western monarch butterflies again.”

In February, the Solano Resource Conservation District partnered with Aquino and other community groups to launch a Mare Island planting event, where volunteers replaced lawn grass with California native plants, like yarrow, aster and coyote mint, that attract pollinators. Sarah McKibbin, habitat restoration manager for the Solano RCD, said it’s part of a larger effort led by California’s Association of Resource Conservation Districts to boost habitat-building projects throughout the state to bring the butterflies back. 

Volunteers gather at a new garden site on Mare Island in Vallejo, Calif. on Feb. 18, 2023, adding California native plant species.Manola Secaira/CapRadio

McKibbin said the goal is to replicate this work in the area to create a “pollinator pathway” — meaning places where monarchs can find sustenance throughout Mare Island.  

“We're hoping that a pollinator pathway will take these open spaces of lawn, which don't provide habitat currently, and [convert] them to drought tolerant native landscape that provides habitat for pollinators and monarchs,” she said. 

When people think of monarch butterflies, McKibbin said the first plant that usually comes to mind is milkweed. But the insects need much more than that to thrive; she added that one aspect of the project is educating residents on other native plant species that can help. 

“A lot of people think monarchs need milkweed, which they do, but that's for the caterpillars,” she said. “The monarch butterflies need nectar during the winter while they're in reproductive diapause, and nectar is what sustains them.”

Besides, monarchs aren’t the only endangered pollinators in California. Angela Laws, an endangered species conservation biologist with the Xerces Society for Invertebrate Conservation, said many butterflies, bees and other pollinator populations have seen diminishing numbers. 

A monarch butterfly is perched on a showy milkweed leaf — a plant which is native to much of the West coast, including California — in Sacramento, Calif. in August 2021.Courtesy Eric Laws

“It's not just about planting milkweed,” Laws said. “It's about planting a variety of plants that can support a variety of species.” 

As a rule of thumb, Laws said, Xerces doesn’t recommend planting milkweed within five miles of the coast or overwintering sites, since the plant did not usually grow in those ranges historically. If a person is interested in planting milkweed, she added, it’s important they plant one that’s native to the area, rather than foreign species, like tropical milkweed. 

Laws said she also encourages people to learn more about other native species they can plant at home. If someone buys a native plant from a nursery, she said it’s important to know if any pesticides have been used to grow it and how that could impact pollinators. 

In her own shady backyard in Sacramento, she said she has planted coyote mint.

“As soon as it blooms, I get butterflies, and I have seen monarchs on it regularly,” she said. “It's just a great butterfly magnet.” 

Aquino said it’s important for people to know that they can help in small ways, even if they’re not part of a larger project. 

“You don't have to do a lot of things,” she said. “You can just plant one plant, one California native — if that's all you can do, that is helpful.”