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  • Napa Valley Marketplace Magazine

All Hail the Monarch

by Kathleen Reynolds

The vividly colored monarch butterfly is recognizable by its large size of 3½ -4 inches, its deep orange wings with black borders and veins and the tiny white spots that dot its perimeter. While a delicate and graceful insect, it is also capable of traveling 3,000 miles to overwinter in favorable habitats.

It may also become an extinction statistic.

According to the National Wildlife Federation, the western monarch population has declined by over 80% since the 1990s. The most significant impacts to monarch butterflies come from the loss of habitat for breeding, migrating and overwintering. In addition, indiscriminate use of chemicals to control insects and weeds can have harmful unintended consequences for monarchs; a changing climate is making some habitat less suitable and forcing changes in migratory patterns; and monarchs face many risks from natural enemies such as predators, parasitoids and diseases.

The Monarch Joint Venture is an organization focusing on the conservation, education and research needed to rebuild and safeguard monarch butterfly and pollinator habitats across the country. Western Program Coordinator for the Monarch Joint Venture is Erin Arnsteen. We spoke to her about the importance of monarchs.

“Monarchs are what we call a flagship species for conservation,” said Erin, whose interest in insects started as a child and for monarchs when she and her husband became organic farmers. “This means that monarchs are well-known and very likable, so people are more likely to get involved in working to protect them. By promoting habitat restoration for monarchs, other pollinators and wildlife species also benefit.”

“It’s important to notice and act on the fact that the monarch populations are declining because monarchs are also an indicator species, which means that because monarchs need the same habitats (native milkweed and other nectar flowers) as many other pollinators, and even other wildlife, and many people are paying attention to monarchs, they are an indication of what’s happening to other lesser-known species. Therefore, if monarchs are in trouble because they don’t have enough habitat, then many of our other native pollinators and wildlife that share their habitat are in trouble as well. Because they are so well known and their decline is easy to see, monarchs are like the proverbial ‘canary in the coal mine’ for pollinators.”

Can monarchs be seen in Napa County and if so, when?

“Yes, monarch butterflies do visit Napa County. The Monarch Joint Venture collaborated with other partner organizations to develop the Priority Action Zones Map for Monarch Butterflies. Napa County falls in the Priority 1 Action Zone, which means we can see monarchs early in the season as they leave their coastal overwintering sites seeking food, mates and milkweed, during the mid-season as they feed, mate and lay eggs on milkweed plants and late in the season as they feed and fly back to their overwintering sites along the coast. With a warming climate, monarchs may now be active in our area any time between February through early December. I see the most monarch activity in my garden between late July and late September.”

Erin will present a program on monarchs through the Yountville Parks and Recreation Department on Tuesday, October 17, from Noon to 1:30 at the Yountville Community Center. For more information, visit or call (707) 944-8712.

“For the program, I will be covering the monarch life cycle, migration and monarch mimics (butterflies that are often mistaken for monarchs) and their host plants, so community members can more easily identify monarchs and understand what else they can plant to attract even more butterfly species.”

Erin co-founded the Western Monarch Society of Napa County in 2020 with the main goal of growing more locally native habitat for all pollinators with a special focus on monarch butterflies. Over the past three years, they have grown and given away approximately 25,000 native milkweed plants to community members and farmers in Napa, Mendocino, Lake and Yolo Counties. She runs the Monarchs & More Western Habitat Program at Monarch Joint Venture, which provides native monarch and pollinator habitat at a larger scale and spans the entire state of California and Southern Oregon.

Where can locals find milkweed plants for the monarchs?

“The Western Monarch Society of Napa County gives away free organically grown native milkweed plugs each spring and early summer at the St. Helena Farmers Market and sometimes at the Napa Farmers’ Market while supplies last. Folks can visit to see when the giveaway will be next Spring. Otherwise, a few other local places to get organically grown native plants are the Napa Valley Chapter of the Native Plants Society Native Plants Sale which usually occurs in April or, if you’re up for a short drive, there are a couple of nurseries that specialize in California native plants and carry native milkweed: California Flora Nursery in Fulton, Oaktown Nursery in Berkeley and Watershed Nursery in Richmond. Places to get seed are Larner Seeds in Bolinas and Hedgerow Farms in Winters.”

There are several important things about monarchs that Erin wants people to know.

1. It is illegal to handle monarchs in the state of California without a special permit. This includes any life stage egg, caterpillar, adult butterfly and any type of movement or alteration, so you should not bring caterpillars inside your home, rear caterpillars or even put cages around plants to protect caterpillars.

2. Milkweed is the only plant the monarch caterpillar will eat, plant it and let it be eaten by caterpillars. Don’t apply any pesticides (organic or otherwise including neem oil) on the milkweed because this can have the same effects on the caterpillars as the insects you’re trying to eradicate.

3. Plant only milkweeds that are native to our area. Do not plant tropical milkweed (Asclepias curassavica and Asclepias tuberosa) in Napa County. Native species are already adapted to our local climate and die back in the winter, whereas tropical varieties tend not to die back during our mild winters. If the plant material is left to grow through the wet winters, these plants can harbor bad bacteria and protozoa that linger on the plants because they don’t die back. When a caterpillar comes along the following season, it could ingest that bacteria and develop a nasty disease that can cause growth deformities and death in monarchs. More about this at

“I have several suggestions to make a direct impact for monarch butterflies in our area. Please help us create native monarch and pollinator habitat at scale and please participate in or donate to the MJV Monarchs & More Western Habitat Program (M&MWHP). Individuals interested in participating in the M&MWHP must have 1/4 acre to dedicate to pollinator habitat and can submit an interest form online. If you don’t have a large space for habitat, please consider donating to the M&MWHP. We want to make this program self-sustaining for years to come so that we may provide the highest quality regionally appropriate plants for monarchs and other pollinators for future generations. Donations can be made specifically to the Monarchs & More Western Habitat Program and this money will go directly to planting more habitat throughout the entire state of California including right here in Napa County. For details on donations and other information, check the website”

“Because monarchs may be in our area for so many months out of the year, it is essential that we provide healthy habitat for them at all stages of their life. This means having native blooming flowers from which they eat the nectar and milkweed for their caterpillars to eat.” ~ Erin

Some of her favorite native nectar flowers by season:

Early Manzanita • Ceanothus or “Buck Brush” • California Buckeye


Coyote Mint • Black Sage & Gumplant

Late California Aster • California Goldenrod • Coyote Brush

There are 4 species of milkweed native to our area here in Napa County that caterpillars will eat (adults will also feed off the nectar of these diverse species): Heart Leaf Milkweed, Narrow Leaf Milkweed, Woollypod Milkweed, Showy Milkweed and Heart Leaf Milkweed.

The best time to plant milkweed seeds and plants is in the late fall right before the first rains so the plants and seed can acclimate to the local temperature changes and take advantage of winter rain. Seeds need to experience the cold temperatures of winter to grow, a process called stratification. If you have irrigation, milkweed plants can be planted anytime in the spring after the final frost through the fall before the first frost. Native milkweed is a deciduous perennial and will lose all its leaves in the late fall, go dormant in the winter, and reemerge in the spring. Once the plants lose all their leaves, cut the stems down to about 3 inches from the ground to prevent any bacteria from growing on overwintering stems, which could be harmful to next year’s caterpillars.


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