The western monarch population is crashing, but home gardeners and the Laguna Foundation are here to help
Sonoma County Master Gardener Suzanne Clarke has been raising monarch butterflies for over 20 years, so when she learned that the population of monarch butterflies in the western United Stated had declined by 84% last year, she took it personally.
“I was an elementary school teacher, and I had them in the classroom and started every September that way, which is a great way to get kids really interested in learning,” she said.
This Saturday, Clarke will be giving a talk at the Sebastopol Library about the plight of the monarch and what the home gardener can do to help their survival.
A monarch primer
“One of the important things to know is that there are actually two distinct monarch populations. The dividing line is more or less the Continental Divide. The East Coast monarchs are the ones that go to Mexico,” Clarke said, noting that she traveled to Mexico to see them for the first time this year in February. “The ones west of the divide overwinter in California.”
“They’re migratory creatures,” she said. Both populations fly north into Canada during the summer months and then fly south again in fall.
Most people are familiar with the monarch’s life cycle — egg, larvae, chrysalis, adult. There are four generations in a year. Monarchs emerge from their chrysalis in late spring and live just two to six weeks but before they die, they start the cycle over again. Ditto for the second and third generation. The fourth generation is different. Born in September and October, it migrates south, lives through the winter — sometimes six to eight months — and starts the cycle all over again in spring.
“One of the interesting things about monarchs is they’re one of the few butterflies that overwinter as adults, rather than as a chrysalis,” she said. “That’s why you hear about them roosting together in a clump when it’s chilly; they warm themselves that way.”
The role of native milkweed
As most American school children know — thanks to teachers like Clarke —monarch butterflies lay their eggs on one plant: milkweed, a meadowland plant that grows in profusion throughout the United States, providing a traveling buffet and egg depository for monarchs. There are over a 100 species of milkweed in North America.
Clarke said that butterfly experts are asking gardeners across the country to plant milkweed that is native to their particular region, interspersed with nectar plants that provide food for adult monarchs.
There are two milkweeds native to Northern California, showy milkweed and narrowleaf milkweed, Clarke said.
Maggie Hart, outreach manager for the Laguna de Santa Rosa Foundation, said that the foundation staff and volunteers have planted hundreds of milkweed plants at the Laguna Wetlands Preserve and Laguna Uplands Preserve to support monarch habitat.
They chose to plant California narrowleaf milkweed (Asclepias fascicularis), which, according to Hart, “has a wider native range and a whole lot more garden tolerance than most of the other native species.”
“Narrowleaf milkweed is a perennial with a three-foot-tall stem and large (but narrow) five-inch leaves and a five-inch or so flower cluster. In our area, this plant is covered with monarch caterpillars during the summer,” Hart wrote in an email, noting that orioles use the milkweed’s dead stems for nests the next spring.
There are a couple of reasons for seeking native milkweeds as opposed to the more commonly available commercial varieties, such as tropical milkweed.
According to Hart, the scientists at the foundation say that “the alkaloids associated with this (narrowleaf) milkweed and other milkweeds give the monarch and other butterflies that feed on it protection from predators. Alkaloids from the wrong milkweed (South American, Mexican, etc.) can expose the butterflies to predation. If the monarch or other butterfly has not evolved with the milkweed, they may have limited tolerance for the particular alkaloid or latex of the plant species.”
Clarke said the wrong variety of milkweed can also give the wrong type of signal to fourth-generation monarchs, causing them to lay eggs in fall rather than spring — dooming the next generation of eggs and caterpillars to a cold death in winter.
If you happen to have tropical milkweed in your yard already, there is something you can do to make it more Monarch friendly, Clarke said — quarterly pruning. (Learn the details from Clarke at her talk on Saturday.)
Sebastopol commits itself to monarch protection
At its meeting on Tuesday evening, the Sebastopol City Council honored the Laguna de Santa Rosa Foundation’s efforts to restore monarch habitat by planting native milkweeds and nectar plants in multiple preserves.
Mayor Neysa Hinton has also signed the National Wildlife Federation’s Mayors Monarch Pledge, committing to create habitat for the monarch butterfly and other pollinators and to educate citizens about how they can make a difference in the creatures’ survival.
Causes of the monarch decline
No one really knows why the western population of monarchs had such a precipitous decline in 2018, going from a population of 189,000 one year to 28,500 the next.
Clarke said that some people think that some of the western monarchs simply joined their eastern cousins that year, traveling to Mexico down the butterflies’ eastern flyway. That would also explain why there was a 144% increase in the number of overwintering monarchs in Mexico that same year.
But there’s a more apocalyptic explanation as well. A butterfly parasite called OE (short for Ophryocystis elektroscirrha) is making its way northward along the monarch’s California flyway. An infected monarch can infect a milkweed plant, which then poisons the larvae that feed off it after hatching.
“The caterpillars that eat it, oh, they look awful,” Clarke said. “They turn black and die. Or if they don’t die, they just become unhealthy monarchs, and they can spread the disease.”
She said commercially grown milkweed plants, such as tropical milkweed, are more likely to be infected than locally grown native varieties — another reason to seek out natives.
She also credits climate change for playing havoc with the butterfly’s life cycle and the lifecycle of the plants it depends on.
Like the gardener she is, she is keeping her eye on her garden in Petaluma as a measure of what the future holds.
“I’ve only seen one batch of monarch eggs laid in my garden this year,” she said. “Normally we have more.”
At the Laguna de Santa Rosa Foundation, they are hoping their milkweed efforts will pay off in butterflies this season.
“We just saw the first monarch of the season last Friday flying around outside Heron Hall,” said Dr. Wendy Trowbridge, director of restoration and conservation science programs for the foundation.
She invited the public to come out and see the butterflies at the preserve this fall, and said next spring they will host a volunteer day to plant more milkweed.
Attend Clarke’s talk, “Can the Monarch Butterfly be Saved from Extinction?” on Saturday, Sept. 7, from 10:30 a.m. to 12:30 p.m. at Sebastopol Regional Library, 7140 Bodega Ave., Sebastopol.