If you’ve been out in the arb lately you probably experienced the nostalgic feeling of seeing soft white seeds floating across your path. No, they’re not oversized dandelions but instead one of a group of prairie plants will the common name of milkweed. There are more than 2,000 species of milkweed in the world but only three of them are common to the arboretum: common, butterfly weed, and whorled.
The monarch butterfly lays its eggs exclusively on milkweed because it is the caterpillar’s sole food source. The sap of plants in the milkweed family is poisonous to most animals yet not to monarch caterpillars. Since evolution has allowed the caterpillars to be able to eat milkweed, they can take advantage of toxins in the sap causing the monarch butterflies to be poisonous to predators such as birds. Due to the fact that milkweed is necessary for the growth of monarch caterpillars, it is a popular and traditional plant for butterfly gardens. Even though ingestion of the sap is poisonous to humans, there are many folk medicine remedies that use the sap from milkweed, such as topical treatment of warts. In fact, this characteristic led to its genus name Asclepias in honor of Aesculapius, the Greed god of medicine.
Also of interest is that the fibers inside the seedpod are better insulators than down. In World War II, eleven million pounds of the fibers were collected by the United States for use in lifejackets.
So, next time you’re out in the prairie, open up a pod of milkweed and relive your childhood dreams and if you lose track of time, don’t panic, just snuggle up in warm bed of milkweed.
-- Griffin Williams, for the Cole Student Naturalists
- Watercolor and pen drawing of butterfly weed, Asclepias tuberosa by Sean Dickson '08
- Photograph of monarch butterfly on common milkweed, Asclepias syriaca, by Tom Barnes, University of Kentucky.