Often when we think of the monarch butterfly, the eastern monarch butterfly comes to mind with its spring arrival in the United States and dramatic fall migrations to the mountains in Mexico. Here in California, we are fortunate to host the western monarch butterfly that spends its spring and summers west of the Rocky Mountains and migrates in the fall to the California coast where it stays for the winter, finding protection from frost and storms by clustering together in tree groves.
On its way to the coast, the monarch passes through Marin County to overwintering areas in Stinson Beach and Bolinas. The Coast Miwok recalled stories from their elders of extensive monarch butterfly migrations and vivid orange and black clouds stretching for miles and large enough to obscure the sun.
Unfortunately, over the last 200 years, loss of habitat, use of pesticides, disease, and loss of native milkweed have caused a 97% population decline, placing the butterfly at risk of probable extinction within the next 20-50 years.
In 2021, EAC published a report, Marin’s Monarch Movement, a collaboration with our partners, Marin Monarch Working Group, detailing the challenges the butterfly faces and what we can all do to help.
One critical thing we can do to help monarchs is to plant native milkweed. Monarchs and milkweed enjoy a beneficial symbiotic relationship; the nectar of the milkweed nourishes the butterflies and the butterflies pollinate the milkweed. Monarchs depend on milkweed exclusively for their first life stages.
Planting milkweed is critical for monarchs, but it’s just as critical to know where it’s appropriate to plant milkweed and what type. Otherwise, our good intentions can create other problems that the extremely reduced butterfly population may not be able to cope with.
If you live within 5 miles of the Pacific Ocean, you should focus on planting native nectar plants to help the monarch butterfly.
If you live more than 5 miles from the Pacific Ocean, you should focus on planting narrowleaf or showy milkweed and native nectar plants to help the butterflies.
Unfortunately, many well-intentioned individuals and nurseries over the years have planted and sold tropical milkweed varieties. Tropical milkweed is highly problematic for monarch butterflies, as it encourages adults to breed in the winter (disrupting natural migration and breeding cycles). When it’s planted along the coast, tropical milkweed causes monarchs to continue breeding when the butterflies should be conserving nectar and energy to survive the winter months, and it spreads disease (Ophryocystis elektroscirrha or OE, a protozoan parasite that covers infected adult monarchs in microscopic spores that infect other butterflies preventing them from developing fully).
The sale of tropical milkweed has been a major problem, as the demand by the public to find milkweed to help monarch butterflies means that nurseries are in search of easy to stock options for their customers.
Now, thanks to the advocacy of the Marin Monarch Working Group, the County of Marin announced a ban of the sale of tropical milkweed at all nurseries effective August 24th! Nurseries in Marin will be required to only sell native milkweed varieties including narrowleaf and showy milkweed.
This is an important step to support the western monarch butterfly in Marin County. Native milkweeds are adapted to the life-cycle and rhythm of the butterflies migration as it becomes dormant in the fall. This is a natural signal for the butterfly to make its winter migration to the coast.
Over the next several months, Marin Monarch Working Group partners will be planning to help the local nurseries to ensure that they have enough native narrowleaf and showy milkweed to sell.
For people who have tropical milkweed at home in their garden, now is the time to begin planning to cut it back and to contact our Marin Monarch Working Group partners, the Salmon Protection and Watershed Network (SPAWN) to trade out for native milkweed plants. Contact Audrey for more information on this program at Audrey [at] tirn.org.
