Blue Ridge Naturalist: Butterfly Weed Won’t Save Monarchs

10
1957

I’m often asked how I became so captivated by the natural world. Most people usually answer this question by saying they saw a particularly beautiful animal or plant, which made them want to learn more about it. From there they moved on to other aspects of nature. But I was simply born with a love of all things wild.

I was very young when my grandparents were still alive and owned a farm. Almost every memory I possess of spending time at the farm involves wildflowers and wild animals, even though my family had no interest in nature. (I’m happy to report that changed when I started writing about it.)

No one personally introduced me to the lovely plants and secretive wild animals that weren’t as difficult to spot back then as they are now. My attention was just innately drawn to the natural environment that surrounded my family as we walked along roadways to gather blueberries that were growing wild.

Folks at that time didn’t insist upon roadsides and field borders being cut and manicured as most people demand today—as if unkempt plant growth is somehow undignified and indicative of bad moral character. The Monarch Butterfly is just one of the most obvious casualties of this current attitude towards the natural world.

The Monarch population is estimated to have dropped by a whopping 90 percent over the past 20 years. Farmers in the Midwest contributed to this situation by increasing herbicide usage to make sure no “weeds” competed with crops throughout the growing season. One of those so-called weeds was milkweed—the only kind of plant a Monarch caterpillar can feed upon.

Needless to say, a dearth of milkweed equates to a dearth of Monarchs. Indeed, the U.S. Fish & Wildlife Service is considering adding this butterfly to the Endangered Species list—a shocking turn of events when the Monarch has always seemed so abundantly common as to be safe from the threat of extinction.

Another important factor is the unwillingness of folks to do what’s best for wildlife instead of themselves around their homes. Most gardeners, even those growing “butterfly gardens,” prefer to grow Butterfly Weed (Asclepias tuberosa) rather than Common Milkweed (Asclepias syrica).

People have a fondness for Butterfly Weed because of its lovely orange color and its compact growth habit. Unlike its ungainly cousin—the Common Milkweed with its coarse growth that can reach 5-6 feet in height—Butterfly Weed fits better, aesthetically and size-wise, into a cultured landscape.

But this species presents two serious problems for Monarchs: a less desirable sap for the caterpillars to feed upon, and an ultimate size that is not sufficient for these insects to reach maturity.

The sap of Butterfly Weed is clear, not milky. In other words, it does not contain much of the alkaloids and other complex compounds that make Monarchs distasteful to predators, sickening them to such an extent that they do not try eating a Monarch again.

Surprisingly to me, scientists aren’t concerned about gardeners choosing to grow Butterfly Weed instead of Common Milkweed. They seem to think that as long as a few Monarchs are eating more-chemically toxic milkweeds somewhere else, the rest (i.e., the ones feeding in your yard) will be adequately protected.

It’s very common for scientists to take the attitude that getting people to do anything at-all-positive for wildlife is acceptable because otherwise people might instead do nothing. While I certainly want to encourage folks to do whatever they can to make their yards more nature-friendly, even if the choices they make are not the best ones, this particular instance is different. I can’t support the allowance of Butterfly Weed as a suitable plant to assist diminishing Monarch numbers.

People need to know that if most Monarch caterpillars feed upon Butterfly Weed, most Monarch caterpillars will be more palatable than they would be if they fed upon Common Milkweed, and that puts the entire population at risk of predation. Indeed, when I look to Mother Nature—as I always do—she backs me up. (The natural world can always be counted on for verity.)

The most-common and most-used milkweed from the Great Plains eastward in the United States and north to southern Canada—the range of the Monarch—is Common Milkweed, with its milky sap. If the scientific supposition that Butterfly Weed is just as good a plant for Monarchs as Common Milkweed were valid, you would expect Butterfly Weed to be more common than it is throughout much of its, and this butterfly’s, range.

To me, this provides the definitive proof that the Common Milkweed is the one that has been used the most throughout the centuries by Monarchs, and that should be reason enough to pick this species for your garden. But if you are skeptical of my assertion, I can give you the undeniable evidence for not choosing Butterfly Weed: The plant is so small that it simply can’t support one caterpillar, let alone many, all the way to maturity.

Unless you can grow a huge number of these plants in your garden, you will doom Monarch caterpillars to starvation. I know because my husband was kind enough to rescue many caterpillars one year from a person’s garden that held only Butterfly Weed. Every one of those Monarchs would have died if I hadn’t been growing Common Milkweed in my gardens.

Indeed, Monarch butterflies themselves have provided the indisputable substantiation of my contention: They’ve never laid even one egg on the Butterfly Weed growing in the same garden bed as my Common Milkweed.

Monarchs know what they need. If they lay eggs upon Butterfly Weed, you can rest assured that there’s too limited a supply of Common Milkweed in the area. Please use your garden space wisely by planting Common Milkweed instead of Butterfly Weed. Monarchs desperately need you to do what’s best for them, not you.

Note: VDOT has begun a new “Pollinator Habitat Program” to assist pollinators by creating and maintaining appropriate habitat. The agency is looking for partners to work with to create plots on VDOT lands in and near Safety Rest Areas & Park & Rides. The Interstate 64 VDOT Workers Memorial on Afton Mountain is a location they are considering for this program. Garden clubs, wildlife conservancies and area businesses are encouraged to participate by providing volunteer labor and funding. If you’re interested, please contact Diane Beyer, State Roadside Management Planner, at [email protected] for more information.

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10 COMMENTS

  1. Very Good article – one of the very few that points out that the #1 problem is a cultural one; i.e. that in decades past “folks didn’t insist upon roadsides and field borders being cut and manicured as most people demand today.”

    You also did an excellent job pointing out the #2 problem is also cultural: “the unwillingness of folks to do what’s best for wildlife instead of themselves around their homes” hence they plant butterfly weed (Asclepias tuberosa) which monarchs often ignore instead of the common milkweed they love (Asclepias syriaca).

    • Thank you so very much, Paul, for taking the time to write. I deeply appreciate it.

      I don’t always receive support for my efforts, so it’s especially meaningful to me when I do.

      Ever so gratefully,
      Marlene

      • I’m living in a new subdivision that still has vacant land. While out walking the dog, I would notice the Common Milkweed growing in these lots. Unfortunately, they are now mowing these lots in hopes of making the land more desirable to sell. I was saddened to see this happen as we used to have plenty of butterflies. I’m in the process of creating areas in my yard for both the bees & the butterflies. However, I am not able to find Common Milkweed seeds/plants. Do you have any suggestions where I might find these? (I might end up taking a trip to the country to dig some up but am not sure if they transplant well.)

        • Hi Sheryl,

          If you put “common milkweed seeds” into an Internet search box, you should get a listing of several nurseries that sell Asclepias syriaca (Common Milkweed). It’s best to plant seeds, not plants.

          Thanks ever so much for your efforts to help our wildlife.

          Sincerely,
          Marlene

  2. Intesresting article. I’d like to make a couple of points though:

    1. Common milkweed is still largely perceived by the general public
    as a horrible weed- wrongly so. So most would never consider planting it in their yards. Butterflyweed
    offers an “acceptable” alternative, albeit not perfect alternative to common milkweed.

    2. Because of the factors above, common milkweed is not as available
    on a large scale as is butterflyweed. This needs to change if it is to replace
    ButterflyWeed in butterfly gardens.

    3. Butterflyweed is a plant people add to their gardens
    when they’ve made the symbiotic relationship between milkweed and the monarch. Planting it often leads
    to these same people planting other varieties of milkweed including
    common milkweed.

    I certainly agree that Butterflyweed should not be
    THE core milkweed planted for monarchs. But it is for
    a lot of people the ONLY milkweed species they plant. And this is
    better than NO milkweed.

    • Hi James,

      Thank you for writing.

      I just want to say that I wrote this article with the hope that once people understand that Common Milkweed is truly what our disappearing Monarch population needs to rebound that they will want to plant it instead of Butterfly Weed.

      I’d like to think that folks would put aesthetics second to the needs of our wildlife.

      Sincerely,
      Marlene

  3. I have both Butterfly Weed and Common Milkweed in my native plant garden. The Monarchs will always choose the Common Milkweed to lay their eggs. I have never found a caterpillar on the Butterfly Weed.

  4. My sister lives 1 hour northwest of Toronto ON Canada in farmland country and has many amazing gardens on her 2 acre property. In her central butterfly garden she has many large common milkweed plants surrounded by butterfly weed.

    She is currently monitoring a dozen+ Monarch caterpillars as they feed and, interestingly enough, none of them are feeding on the common milkweed. All of them are feeding on the butterfly weed, including the butterfly weed in other parts of her garden 30+ feet away from where the central common milkweed garden is located.

    Should we force Monarch caterpillars to only eat common milkweed by removing all the butterfly weed? Is butterfly weed to be considered as “junk food” for monarch caterpillars?

    Just curious on the findings and thoughts of others on this topic.

    Warmest regards,
    Ruth

  5. Dear Ruth,

    I am sorry for the delay in answering. I only just became aware of your comment.

    I would have to say that your sister’s situation sounds rather unusual. I have not seen Monarchs use Butterfly Weed in my garden, where they prefer Common Milkweed. I have also seen a scientific paper that compared milkweed plants and found that Monarchs in the mid-western part of the US did not use Butterfly Weed as a food plant for caterpillars at all.

    That said, not all large milkweed plants are the Common Milkweed species, and Monarchs do not prefer some of them either. Are you absolutely certain that her plants are Asclepias syriaca?

    As for whether Butterfly Weed should be considered “junk” food, I guess in a way it is because it does not provide protection from predators.

    I would not necessarily suggest removing that species since it has been used in your sister’s garden (although such a short plant seems unlikely to be able to support caterpillars to their chrysalis stage), but I would suggest that growing the actual species known as Common Milkweed would be better.

    If you respond, please write to me at [email protected]

    Thanks so very much for your interest!

    Sincerely,
    Marlene

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