Butterfly Weed Won’t Save Monarchs

 

© Marlene A. Condon
March, 2015

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 diane.beyer@vdot.virginia.gov for more information.