During the Pacific battles of WWII, military occupation of Java eliminated the Allies’ source of kapok, the material that filled life jackets used by soldiers in the war.1 Kapok is a cotton-like, fibrous substance surrounding the seeds of the kapok tree (Ceiba pentandra). Without this critical material to fill life jackets, the United States turned to an abundant native plant with seed carried on the wind by fuzzy, lightweight floss: milkweed (Asclepias spp.). Citizens were asked to collect milkweed pods to fill life jackets with milkweed floss as an effective and life-saving replacement for kapok.

Credit USFWS

The Endangered Species Coalition recently heard an anecdote about the wartime efforts to collect milkweed from community member Kay Keeler: “I grew up in Chicago in a square mile that had streets, elm trees, street lights, sidewalks and fire hydrants, but few apartment building or homes until after WWII.  Milkweed was abundant and during the war we students were asked to pick the pods and bring them to school as they would be used for life-preservers!” Enough milkweed was collected through efforts like these – more than 1.5 billion pods- that 1.2 million life jackets were produced with milkweed as filler during WWII.1

Today, life jackets are produced from synthetic materials, but the essential nature of milkweed hasn’t changed. Milkweed is critical to the lifecycle of the iconic Monarch butterfly (Danaus plexippus). Monarchs rely on milkweed as the sole host plant on which these extraordinary butterflies can lay eggs.

Milkweed leaves are the only food which can be eaten by Monarch caterpillars. Milkweed leaves contain a toxin which makes Monarchs taste terrible to birds and other predators, a strategy allowing this amazing invertebrate to survive. Adult Monarchs also rely on milkweed flowers as a nectar source.

Credit Wikimedia Commons

The loss of milkweed habitat is implicated in the decline of Western and Eastern Monarch populations. Because this plant has the word ‘weed’ in its name, some people worry that the plant is noxious or invasive. However, none of the 100 species of milkweed in the US are classified as noxious2. Milkweed, like many other flowering plants, can spread, but planting the kind of milkweed native to your region reduces spreading and makes milkweed a wonderful and extremely beneficial plant to add to your garden. Monarch butterfly populations have declined by up to 90%, due in part to eradication of milkweed across Monarch habitat. Monarch populations are currently candidate species for listing under the Endangered Species Act, with a decision due in June 2019.

You can help the Endangered Species Coalition in our efforts to increase habitat for Monarch butterflies by providing funding toward the purchase of local, native milkweed. We are working with planting sites nationally to plant milkweed and native nectar plants to help grow habitat and conserve the iconic Monarch butterfly. To donate, visit https://secure.actblue.com/donate/escplants



  1. 1. The Washington Post, P. Clark. Milkweed fruits pods of plenty (September 25, 2012). Retrieved from https://www.washingtonpost.com/wp-srv/special/metro/urban-jungle/pages/120925.html
  2. 2. USFWS. Spreading milkweed, not myths. (April 19,2017). Retrieved from https://medium.com/usfws/spreading-milkweed-not-myths-5df8c480912d

Stay Informed!

1 comment on “Milkweed is a Life Preserver for Monarchs

Leave a Reply

Your email address will not be published. Required fields are marked *