What is Milkweed?

Milkweed is a flowering plant named after a milky latex substance that is exuded when the plant tissues are damaged. Milkweed’s scientific name (genus) is Asclepias, named after Asclepius, the Greek god of medicine.

Narrow-leaf milkweed growing in the wild in Southern California (E. Wallace)

Milkweed is the host plant for monarchs because the caterpillars rely solely on milkweed for food.

The latex in milkweed plants contains cardenolide, a substance that can be toxic if ingested by humans and some animals. It has a bitter taste that most animals will avoid.

Two monarch caterpillars eating native narrow-leaf milkweed. (E. Wallace)

When monarch caterpillars eat milkweed, they ingest some cardenolide, which gives them a protective advantage from predators. If a bird tries to eat a monarch butterfly, the bird will have a bitter taste in its mouth and may throw up.

Even though milkweed plants contain a toxic substance, they are beneficial wildflowers that are important to birds and many insect species. The image below shows milkweed bugs (Oncopeltus fasciatus) enjoying narrow-leaf milkweed flowers.

Milkweed bugs feeding on milkweed blossoms. (E. Wallace)

Endangered bumblebees (Bombus crotchii) are gathering nectar from woolly-pod milkweed flowers in the image below.

Bumblebees (Bombus crotchii) gather nectar from native milkweed. (E. Wallace)

In Southern California, native milkweed plants go dormant in winter and die back to the ground before re-emerging in the spring.

Many nurseries sell non-native, orange-flowered tropical milkweed (Asclepias curassavica) because it’s easy to grow and appealing to the eye. Unfortunately, it has a deleterious effect on monarchs. Scientists have found that tropical milkweed causes monarchs to be under-weight and parasite-ridden.

Tropical milkweed can harm monarch butterflies. (Monarch Butterfly Garden)

If you live in Southern California, resist the urge to buy tropical milkweed.

Instead, search for nurseries that offer milkweed that is native to your area. The healthiest milkweed you can buy in Southern California is narrow-leaf milkweed (Asclepias fascicularis) at Roger’s Gardens in Corona del Mar, or at Tree of Life Nursery in San Juan Capistrano.

This year, Tree of Life Nursery is also selling a beautiful native milkweed called woolly-pod milkweed (Asclepias eriocarpa shown below).

Woolly-pod milkweed. (E. Wallace)

Summertime is a great time to plant native milkweed, and it is one of the easiest things we can do to help monarchs flourish. Visit Roger’s Gardens or Tree of Life Nursery soon and try planting a native milkweed in your yard.

Monarch butterfly at rest. (E. Wallace)

Simple Support for Western Monarchs

Every winter, volunteers travel to western monarch overwintering sites to count butterflies roosting in trees near the coast. Last winter, fewer than 2,000 monarch butterflies were found overwintering along the California coast.

Overwintering monarchs November 2015. (Kathy Keatley Garvey)

Compared to 1997, when it was estimated that more than 1 million monarch butterflies overwintered, the numbers from the 2021 count were historically low.

Emma Pelton and Stephanie McKnight of the Xerces Society write, “Iconic and beloved monarch overwintering sites like Pismo Beach and Natural Bridges reported only a few hundred monarchs during the count. More startling, Pacific Grove, which goes by the name “Butterfly Town, USA” because of its overwintering sites, had no monarchs at all. Each of these sites normally host thousands—in some years, tens of thousands—of butterflies during the winter months, and are locations where visitors travel to experience the marvel of glittery orange monarch clusters.”

Scientists are not sure exactly why the overwintering monarch butterfly numbers were so low last winter, but they know that wildfires, increasing use of pesticides and herbicides, climate change, and habitat loss are some of the culprits. 

Western monarch butterfly. (E. Wallace)

What can we do to help western monarch populations recover? 

Plant native: Plant milkweed that is native to the area where you live. For Southern Californians, you can find native milkweed at Roger’s Gardens in Corona del Mar and Tree of Life Nursery in San Juan Capistrano.

Plant pesticide free: There is a dizzying array of chemicals available to kill insects in your home and garden. But many of these pesticides kill beneficial insects like monarch butterflies as well. The Xerces Society writes:

“‘Pesticide” is an umbrella term that includes—but is not limited to—insecticides, herbicides, fungicides, and rodenticides. Each year in the United States, more than a billion pounds of pesticides are applied across home gardens, parks, and farms to manage unwanted weeds, insects, diseases and other ‘pests.’ The majority of pesticides used are ‘broad-spectrum’ meaning they kill broadly. Contamination resulting from the extensive use of pesticides has been tied to the decline of species important to ecosystems, including pollinators.”

A beneficial insect, the praying mantis, hanging out on a pesticide-free narrow-leaf milkweed. (E. Wallace)

Xerces also writes about the dangers of using herbicides: “Herbicides may kill plants or, in the case of pre-emergent herbicides, prevent plant germination. Herbicides can indirectly impact pollinators and other invertebrates by eliminating habitat. For example, declining populations of the monarch butterfly have been linked to increasing herbicide use—because that, in turn, leads to the loss of milkweed and nectar plants that monarchs rely on.”

Instead of reaching for a pesticide, consider planting a more diverse plant palette in your home landscape to attract beneficial insects and provide support for birds and other predators to pests. To learn more about pesticides, click here.

This video shows a monarch caterpillar climbing on native milkweed, on its way to finding more milkweed leaves. This video is in real time. The caterpillar is speedy! (E. Wallace)

We can all provide a healthy environment for creatures living in our home landscape. A healthy garden will support western monarch butterflies as they seek out nectar this summer. And when a female monarch butterfly finds native milkweed in your yard, she can lay eggs there. Your native milkweed will provide food for caterpillars to munch and grow.

Monarch caterpillars eating woolly-pod milkweed. (E. Wallace)

Monarchs Arrive for Summer

Have you noticed monarch butterflies flying around your California yard this summer?

Western monarch butterflies are an iconic butterflies that delight us with bright orange plumage, black stripes, and white polka dots. They are so large, they cast a shadow when they fly overhead.

After hearing about the historically low overwintering monarch butterfly count last winter, I have been surprised to see a healthy number of western monarchs making daily visits to my home landscape over the past few months. 

Monarch rests on a native milkweed. (E. Wallace)

I am seeing more monarchs than I expected because last winter, fewer than 2,000 monarchs were counted overwintering in California. 

According to Xerces.org, “Early count numbers from Xerces’ Western Monarch Thanksgiving Count suggest that the western migratory population is headed for an all-time low. With approximately 95 percent of the data in, only 1,800 monarchs have been reported…This is a significant decline from the low numbers of the last two years where the total hovered just under 30,000 monarchs. These numbers are a tiny fraction of the millions of monarchs that likely visited overwintering sites in the 1980s and the hundreds of thousands of monarchs that graced California’s coast as recently as the mid-2010s. In fact, this represents an overall decline of more than 99.9% in the migratory population.”

Photo of overwintering Western monarch butterflies by Candace Fallon/Xerces Society

What can we do to help reverse their dramatic decline in numbers?

Monarch caterpillars only feed on milkweed. The first step you can take to help the western monarch butterfly is to plant milkweed that is native to your area. Good native milkweed choices for Southern California include narrow-leaf milkweed (Asclepias fascicularis) and woolly-pod milkweed (Asclepias eriocarpa). 

You can install native milkweed plants now, and support monarch butterflies looking for a host plant to lay their eggs. 

Western monarch caterpillars feasting on woolly-pod milkweed in Southern California. (E. Wallace)

Planting milkweed that is native to where you live is more beneficial than non-native (tropical milkweed) because non-native milkweed often hosts parasites that harm butterflies and disrupts their reproduction and migration.  

One nursery in Southern California is trying to help increase western monarch populations by offering a free trade-in. At Roger’s Gardens in Corona del Mar, you can bring your non-native tropical milkweed into the nursery and receive a free native narrow-leaf milkweed replacement plant.

Another great nursery to buy native milkweed is Tree of Life Nursery in San Juan Capistrano. Tree of Life Nursery has several species of native milkweed plants for sale this year including woolly-pod milkweed shown above.

Monarch caterpillar munching native narrow-leaf milkweed yesterday. (E. Wallace)

Planting plenty of native milkweed in your garden is a great first step in helping the western monarch butterfly populations recover. I will discuss more ways you can help monarchs in my next post. In the meantime, visit your local nursery and buy several milkweed plants for your garden, and while you are outside, look for monarchs cruising your garden.

Where Do Western Monarchs Spend the Spring?

Despite the fact that Western Monarch butterflies are universally loved, their numbers have plummeted in recent years.

Two monarch butterflies cruise together under a Coast Live Oak tree. (Elizabeth Wallace)

What can you do to help? Join the Western Monarch Mystery Challenge–a campaign created to increase awareness of locations where Western Monarchs spend the spring in California after leaving their coastal California overwintering sites.

Male and female Western Monarchs together. Photo by Jeff Wallace.

If you see a monarch from February 18 through April 22, take a photo (it can be far away and blurry). Then report the siting to iNaturalist, the Western Monarch Milkweed Mapper, or email it to MonarchMystery@wsu.edu.

Far away and blurry photo of Western Monarch on baccharis pilularis cultivar and coffee berry. (Elizabeth Wallace)

Your photo will help scientists better understand Western Monarchs’ locations and activities in February, March, and April. When you share your springtime Monarch observations, you help conservation efforts for the butterfly.

In between reporting your spring Western Monarch sitings, plant more native plants in your garden, especially California buckwheat, salvias, manzanitas, narrow-leaf milkweed, and maybe a scrub oak tree!

Butterfly Weekend

This weekend was California Biodiversity Day 2019 sponsored by the California Natural Resources Agency.  Scientists sought observations by fellow scientists, gardeners and ordinary citizens in mapping plants and animals living in California.

Male and female monarchs get together on the leaves of an alder tree to perpetuate the species. Photo by Jeff Wallace.

In honor of Biodiversity Day, I took a break from my chores and spent some time outside in my backyard with my husband to observe the local wildlife. We saw eight different species of butterflies, cactus wrens eating California coffee berries, hummingbirds sipping nectar from California fuchsia, a lizard doing push-ups on our garden wall, and a leaf-cutter bee laying eggs.

A pair of woodland skippers resting on a ceanothus. (Elizabeth Wallace)

After taking these photos, we uploaded them to iNaturalist, a citizen science project and online social network of naturalists, citizen scientists, and biologists built on the concept of mapping and sharing observations of biodiversity across the globe.

Metalmark butterfly at rest. (Elizabeth Wallace)

It’s fun discovering tiny butterflies and native bees that live in the garden.  I spend a lot of time watching the butterflies, wishing they would rest so I can capture their image with my iPhone.

My friend in Costa Mesa noticed Monarch caterpillars had eaten all of the leaves of her two narrow-leaf milkweed bushes this week.  She was alarmed and worried the caterpillars would need more food.  She drove to Armstrong Nursery on Thursday and purchased a large narrow-leaf milkweed and her Monarch caterpillars are happily munching away once again.  They are hungry!

Monarch caterpillar feasting on a narrow-leaf milkweed. Photo by Cynthia Grilli.

Scientists were concerned because the annual Western Monarch butterfly count was historically low this year (fewer than 30,000 butterflies were counted–down 99 percent from the 1980’s).  They fear the Western Monarch may be nearing extinction.

It feels hopeful to see these chubby caterpillars, and the two adults mating in my garden this week.  If you would like to learn more about how you can help Monarchs, go to The Xerces Society.

Simple Ways to Make Your Garden Good for Butterflies

Bringing local wild land plants into your garden will increase the number of butterflies inhabiting your airspace.

Two monarch butterflies cruising together beneath a Coast Live tree. (Elizabeth Wallace)

For residents in Southern California, gardening with native California plants can be unfamiliar. Most homeowners appreciate the ease of shopping at their neighborhood Home Depot Garden Center, Lowes, and True Value for plants. Unfortunately, it’s difficult to find California native plants at these outlets.

The showy orange-colored, non-native tropical milkweed is available from local retailers like Home Depot, but tropical milkweed is not healthy for adult monarch butterflies in Southern California.

Why Native Milkweed

Native milkweed for sale at Rogers Gardens in Corona del Mar, California. Photo by Ron Vanderhoff.

Tropical milkweed (non-native) hosts a protozoan parasite that harms adult monarch butterflies in Southern California.

To help increase monarch butterfly populations, plant milkweed that is native to your area. In Southern California, narrow-leaf milkweed (Asclepias fascicularis) is one of the best species of milkweed to support monarch butterfly populations.

Narrow-leaf milkweed

Narrow-leaf milkweed (Asclepias fascicularis) growing in the wild at O’Neill Regional Park in Southern California. (Elizabeth Wallace)

You can find native milkweed at nurseries that grow or source California native plants. Tree of Life Nursery  in San Clemente is the largest grower of California native plants in the state. Roger’s Gardens in Corona del Mar also sells California native plants that are safe for birds and butterflies.

Tree of Life Nursery

Fall flowers for pollinators at Tree of Life. (Elizabeth Wallace)

When you visit Tree of Life Nursery, you can choose among thousands of California native plants that are all beneficial to birds and butterflies.

In the next post, I will talk about some of the easiest California native plants to grow in your garden, including the California buckwheat of course!

California buckwheat

California buckwheat growing in a home garden. (Elizabeth Wallace)

If you would like more information about butterflies, including monarchs, visit The Xerces Society.