Wednesday, June 30, 2021

Some Uncommon Things About Common Milkweed

Common Milkweed, Asclepias syriaca, blooming on June 30, 2021, at Crow Hassan Park Reserve in Minnesota.

 

At times reviled as a nuisance of farm fields and pastures, Common Milkweed (Asclepias syriaca) has gained new respect as a plant that supports Monarch Butterfly larvae. That’s just part of the story, though. Here are a few things about milkweed that get less attention.

  • The plant’s scientific name, Asclepias syriaca, is centuries old. It was given by Carl Linneaus, the Swedish botanist who in the 1700s developed the binomial system of nomenclature. That's the system that gives plants and other living things two names: a generic name – Asclepias, in this case – and a specific name, also called a specific epithet –syriaca for Common Milkweed.
  • Linneaus is said to have been so impressed by the many medicinal uses of common milkweed that he named the plant after Asklepios, the Greek god of medicine. The specific epithet, syriaca, is from Linneaus’ mistaken belief that the plant came from Syria.  

  • Syria is a long way from where common milkweed is naturally found. The plant is native to the Eastern and Great Plains regions of the U.S. and adjacent provinces of Canada. Like many plants, however, common milkweed has found its way overseas. It is now also found in southern and central Europe, where it invades grasslands and farm fields (1).

  • One reason the plant isn’t always welcome is because it’s toxic to many animals, including humans. Like other milkweeds, the plant’s white latex contains cardiac glycosides, compounds that affect the function of the heart. Depending on the amount consumed, milkweed latex can cause symptoms ranging from nausea and vomiting to slowed heart rate, coma and even death (2).

  • Some animals can eat milkweed safely. Milkweed bugs, for example, can isolate the cardiac glycosides they consume while they munch on leaves and other plant parts. The insects themselves then become toxic, which makes them unpalatable to predators. Their bright colors warn potential diners that eating them would be a mistake (3).

  • Evidently, milkweed bugs have a lot of company. According to the U.S. Forest Service, common milkweed is a “mega food market” that feeds more than 450 kinds of insects. Some, like milkweed bugs, are destructive, but others merely sip the plant’s nectar or suck out its sap (4).

  • Medicinal uses of common milkweed have waned, but not long ago, the plant saved lives in a different way. During World War II, milkweed pods were collected for the silks attached to their seeds. The buoyant, waterproof strands, called milkweed floss, were used to stuff life preservers when kapok, another plant fiber used for that purpose, could not be obtained from Indonesia.

  • Milkweed floss was in such demand that school children were paid to gather the pods. The going rate was15 to 20 cents per onion bag or gunny sack filled with pods. Two bags provided enough floss to make one life preserver.

  • Although it’s hard to imagine milkweed floss making much difference in the effort, the plant was abundant enough to have made an estimated 1.2 million life preservers. Milkweed was so valuable that the U.S. government considered it a “wartime strategic material” (5).

  • After the war, common milkweed lost its status and was once again considered a weed. From reviled to revered and back again, shifting fortunes seem to define milkweed’s history.

References

(1) Asclepias syriaca (common milkweed). CABI Invasive Species Compendium. Viewed 6/30/21 at https://www.cabi.org/isc/datasheet/7249.

(2) Milkweed Plant Can Cause Serious Poisoning. Poison Control, National Capital Poison Center. Viewed on 6/30/2021 at https://www.poison.org/articles/milkweed-can-cause-serious-poisoning-204.

(3) Common Milkweed Insects. Susan Mahr, University of Wisconsin-Madison. Wisconsin Horticulture, Division of Extension. Viewed on 6/30/21 at https://hort.extension.wisc.edu/articles/common-milkweed-insects/.

(4) Plant of the week: Common milkweed (Asclepias syriaca).  David Taylor. U.S. Forest Service, USDA. Viewed on 6/30/2021 at Common Milkweed (fs.fed.us).

(5) A weed goes to war, and Michigan provides the ammunition. Gerald Wykes, from Michigan History magazine. Posted February 4, 2014, and updated January 20, 2019, on MLive. Viewed on 6/30/2021 at https://www.mlive.com/news/2014/02/a_weed_goes_to_war_and_michiga.html


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