Milkweed and Monarchs

Monarchs Overwintering in Monarch Grove, Pismo Beach, CA, Photo by Kathy Vilim

Monarchs Overwintering in Pismo Beach, CA, Photo by Kathy Vilim


2013/2014 Winter in California~

Hundreds of orange wings take flight in the afternoon sunshine, cruising on a warm breeze~ Monarchs are leaving the shade of tall eucalyptus trees in the groves where they roost.  There are a handful of overwintering spots for Monarchs in the Central Coast of California, from Pismo Beach north to Santa Cruz.  Unlike their east coast cousins, these monarchs come down from Canada and the Pacific Northwest to California’s Central Coast to overwinter instead of traveling to Mexico proper. The California Flyway extends from Canada down to Baja.

Although East Coast and West Coast Monarchs are of the same species, the Milkweed to which they’ve become accustomed is quite different. They have become adapted to different local species of Milkweed, Asclepias. You cannot plant the same species of Milkweed for the Monarchs of the West Coast as for those East of the Rockies.

It is important to plant Milkweed for the Monarchs, as it is their host plant. Females will be looking for Milkweed to lay their eggs (even right now) on their return north from their overwintering grounds.  But they will need Asclepias that is local to the region.  Local species will bloom at the right time for the Monarchs to leave their roosts.

Monarch Milkweed, Asclepias eriocarpa, Photo  by permission of LasPilitas Nursery

Monarch Milkweed, Asclepias eriocarpa, Photo courtesy of LasPilitas Nursery

The alkaloids associated with specific 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 predators. 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. If you live in the Midwest, you can plant Mexican species (Asclepias mexicana) or Asclepias tuberosa, but don’t plant our species.

Wherever you live in this country, you can plant Milkweed for Monarchs. This is a great list of milkweed species by region. Find yours here:

If you are lucky enough to travel to California in the wintertime, be sure to put the Central Coast Monarch Sanctuaries on your to-see list!  Orange wings begin to fill the air late October, early November, as Monarchs fly in from points north and from inland areas.  By February, they will have left the groves, the females anxious to deposit their eggs on Milkweed plants, fulfilling their life cycle. Here are some of the best CA Coastal groves to look for from north to south (

  1. Natural Bridges State Park, Cliff Drive, Santa Cruz
  2. Monarch Grove Sanctuary, Lighthouse Ave, Pacific Grove
  3. Andrew Molera State Park, Big Sur, 30 miles south of Pacific Grove
  4. Butterfly Grove, Coast Hwy 1, Pismo Beach
Monarch Sanctuary, Pacific Grove, CA, Photo by Kathy Vilim

Monarch Sanctuary, Pacific Grove, CA, Photo by Kathy Vilim

According to  the Western Monarch Thanksgiving Count,  the number of West Coast Monarchs are holding steady (though not nearly what they used to be in the 1990’s). The Monarch Grove Sanctuary (2.5 acres) in Pacific Grove, CA reported 13,000 Monarchs there this 2013/2014 season.

I have visited this overwintering site and can tell you that the monarch grove is indeed magical.  It has just the right amount of sun & shade, monarch-friendly breezes, moisture, tall pines & eucalyptus (their favorite roosting tree), as well as open meadows of native plants & grasses.  It is amazing how they find this place, flying as high as 10,000 ft to land in this grove.

On my visit to Pacific Grove, Monarchs would flit past my face as I walked from my car to the sanctuary.  They were everywhere for blocks around, not sticking to their assigned refuge.  They seemed to know that in wintertime, they own this town! The citizens of this butterfly-friendly town even have signs posted warning of heavy fines for anyone caught interfering with the monarchs or their grounds!  Yay!

Monarch butterfly larva feed on Asclepias speciosa, Showy Milkweed, Photo by LasPilitas Nursery

Monarch butterfly larva feed on Asclepias speciosa, Photo by LasPilitas Nursery

Now, if you are lucky enough to have a garden in California, you will want to add Milkweed to your garden. Find a source of local native milkweed plants and plan to get them as soon as they are old enough for transplant. It may be a little too early to find milkweed plants in most native plant nurseries, as they are still growing.

There are many varieties of milkweed in California. You want to find the ones that are right for your region and growing conditions:

Mexican Whorled Milkweed (Dry climates); Showy Milkweed (Savannahs and prairies); Desert Milkweed (Desert regions); California Milkweed (Grassy areas); Heartleaf Milkweed (Rocky slopes incl Coastal); Woolly Milkweed (Dry deserts and plains)

When you Garden for Monarchs, you are helping restore some of the habitat these butterflies have lost to development and pesticides. Gardening for Monarchs means being mindful of a healthy environment that includes using NO pesticides. Watching these amazing orange-winged creatures in your garden is YOUR reward.

© 2014, Kathy Vilim. All rights reserved. This article is the property of We have received many requests to reprint our work. Our policy is that you are free to use a short excerpt which must give proper credit to the author, and must include a link back to the original post on our site. Please use the contact form above if you have any questions.

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  1. D. Neafsey says

    “Local species will bloom at the right time for the Monarchs to leave their roosts.”

    -What does milkweed bloom time have to do with monarch migration? Monarchs take nectar from all kinds of flowers, native or non-native. The A. syriaca in my region (MA) typically finishes blooming before any Monarchs make it up here.

    I’m not aware of any evidence that monarchs are intolerant of alkaloids from non-native species of Asclepias, or that consumption of non-native Asclepias exposes them to enhanced predation.

    This post is a great cause, but I think it would be more helpful if the rationale for planting or not planting various Asclepias species were more clearly explained. Those who live in sub-tropical climates are advised not to plant A. curassivica because it could naturalize and disrupt migrations, but planting A. curassivica in zone 7 or below is unlikely to negatively impact monarchs, correct?

  2. Karin Steinhauer says

    Interesting question as to whether or not to plant the non native species here in So Cal. Last year I had LOTS of Monarchs well into December and dozens of cats. I have A. currassavica and A. fasicularis planted. The Monarchs overwhelemingly laid eggs on the A currassavica. This year I had only 2 monarchs in the yard and only one cat that I witnessed successfully metamorphisize in to a butterfly and they came in late December/January when the native milkweed had died back. I have asked several people their opinions on whether or not I shoudl remove the A. currassavica. I’ve been told to remove it or to cut it down when the A. fasicularis dies back. I have read the same statement that they must feed on the native milkweed to their area. I have also been told that a cat will usually only continue to eat the same type of milkweed that it started out eating when it hatched but the female will lay on any milkweed. The ones here definitely prefer the non native over the native for laying. My question is with the weather changing so dramatically here (80F in Dec, Jan) should we continue to plant the A currassavica if the Monarchs are going to change their migration times to adapt to the changing climate? I have also planted A. speciosa and am trying to germinate some A californica seeds.

    • says

      I would not plant the non-native tropical because of climate change worries. I have heard there is a problem with the so american milkweed’s longer lifespan affecting the monarch’s migration. Once they lay their eggs, there is no reason to fly north. I have heard monarchs are drawn to the non-native, like candy. There are plenty of reasons to “just plant native” and it is likely this holds true for the monarchs’ world. Thank you for your in depth comment. I am interested to hear how things go.


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