Monarch butterflies and great ways we can help them

Monarch butterfly (Danaus plexippus). Photo: Elaine Miller Bond
Monarch butterfly (Danaus plexippus). Photo: Elaine Miller Bond

Last November, Berkeleyside published an article about a spectacular natural phenomenon seen in Berkeley for the first time: hundreds of monarch butterflies were clustering in the trees of Aquatic Park.

This fall, thoughtful reader and independent gardener Toni Cox wrote to Berkeleyside, requesting that we create a new article about monarchs.

In particular, Cox noted that these beloved, once ubiquitous butterflies are “struggling” — that a decision on whether monarchs will receive protection under the Endangered Species Act will occur by 2019.

Read about Elaine Miller Bond and see her other nature stories on Berkeleyside.


More about the petition for federal protection for monarchs is available from the Center for Biological Diversity, one of the organizations that filed it.

Here in California, numbers of overwintering monarch butterflies have seen an approximate decline of 74% since the late 1990s, according to Emma Pelton, Conservation Biologist for the Xerces Society and its Endangered Species Program.

“While we have seen good numbers of monarchs in the Bay Area in recent years,” Pelton said, “the overall number of monarchs overwintering in California is still far below historic levels.”

There are some great ways to help these beautiful butterflies, Pelton added.

One of them is to plant milkweed — the monarch’s so-called “host plant” — the only plant it eats as a caterpillar and upon which it lays its eggs.


Before planting, however, there are a few caveats. Pelton said that the Xerces Society recommends planting only native milkweeds.

Showy milkweed (Asclepias speciosa), a California native, in bloom. Notice the striped caterpillar atop the flowers on the right? That’s a monarch! Photo: Elaine Miller Bond
Showy milkweed (Asclepias speciosa), a California native, in bloom. Notice the striped caterpillar atop the flowers on the right? That’s a monarch! Photo: Elaine Miller Bond

Nonnative tropical milkweeds, by contrast, can pose dangers to monarch butterflies.

According to Distinguished Professor Arthur M. Shapiro from the Department of Evolution and Ecology, College of Biological Sciences at UC Davis, tropical milkweeds “never created a problem” until just a few years ago, when monarchs began breeding on them in winter.

“Given the lack of native milkweeds in winter,” Shapiro said, “the same individual [tropical milkweed] plants in gardens get used over and over again and as a result (at least in SoCal), get contaminated with a microbial parasite known as OE.”

In monarch butterflies, OE (Ophryocystis elektroscirrha) reduces survivorship and routinely interferes with reproduction, according to Shapiro.


Close-up of a monarch caterpillar on showy milkweed. Photo: Elaine Miller Bond
Close-up of a monarch caterpillar on showy milkweed. Photo: Elaine Miller Bond

Another “rule of thumb,” said Pelton, “is don’t plant milkweed within five to 10 miles of the coast.”

Historically, milkweed grew in the East Bay, but not along much of the Pacific Coast. So even native milkweed, when it is planted too close to the ocean, may disrupt normal breeding cycles, according to Pelton.

Milkweed aside, Pelton said that “important steps” for monarchs include the reduction or elimination of pesticide use and the planting of native nectar plants — plants that may be as beautiful as the butterflies themselves.

Helpful resources:

The Xerces Society list of native nectar plants by region (available soon).

The Xerces Milkweed Seed Finder

For free seeds of California native showy milkweed (Asclepias speciosa): Please prepare a double-stamped self-address stamped envelope with the number of seeds to be grown written on the envelope. Mail it to:

Toni Cox
c/o Berkeley Methodist United Church
1710 Carleton Street
Berkeley, CA 94703

According to Bart O’Brien, Botanic Garden Manager of the Regional Parks Botanic Garden, autumn, particularly October, is a good time for planting milkweed. Springtime works as well, though plants may require more watering in summer.

Monarch feeding on a nonnative plant, red valerian (Centranthus ruber). Photo: Elaine Miller Bond
Monarch feeding on a nonnative plant, red valerian (Centranthus ruber). Photo: Elaine Miller Bond

Looking to see monarch butterflies in Berkeley?

Last week, monitors with the Xerces Society counted 35 monarchs in Aquatic Park. Time will tell whether their numbers will increase to levels seen in the fall of 2015.

Special thanks to all who are mentioned in this article as well as to Mia Monroe, Lawrence Ray, and Alan Kaplan.

Elaine Miller Bond is the author and photographer of ‘Running Wild,’ a new children’s board book from Heyday Books. Forthcoming books in the collection include ‘Living Wild’ (spring 2017) and ‘Wild Colors’ (projected for 2018).

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