Pick a Weed, Save a Life

Milkweeds contain various levels of cardiac glycoside compounds or cardenolides, which render the plants toxic to most insects, animals and humans. Despite their seemingly sinister sap, milkweeds breathe life to pollinators and people alike.

These wildflowers were formally identified by taxonomist, Carl Linnaeus in 1753, who named the genus Asclepias, in honor of Asklepios, the Greek god of medicine. Across the Americas, milkweed was used as a common folk remedy to treat an array of ailments and it remains an active ingredient in traditional medicines today. The liquid latex, which seeps from the plant’s pods, stems and leaves, was often painted on warts to remove them. The roots were chewed on to cure dysentery; and salves and infusions were concocted to ease swelling, rashes, coughs, fevers and even lung diseases. Milkweed was also a popular antidote for Native Americans and conquerors of the New World with a bad case of sweet tooth. High in dextrose, the nectar was enjoyed by many as a source of sweetener.

Milkweeds have fleshy, pod-like fruits that split when mature. Each milkweed seed is attached to ‘pappus’, silk, or floss, that aid in wind dispersal for germination. These fluffy filaments possess natural insulative properties due to their wax coatings. In 1790, an Italian voyager by the name of Lugi Castiglione, observed how mountaineers in Virginia constructed cloth from the milkweed plant to stay warm and dry. During the 1860s in Salem, Massachusetts, there was a booming milkweed industry. Factory workers stuffed seeds into pillows, cushions and mattresses, and even found the plant material desirable enough to produce purses and socks. The United States military later discovered that milkweed floss was five or six times as buoyant as cork and six times lighter than wool. During the last two years of World War II, 25 million pounds of milkweed pods were picked to fill 1.2 million naval life preservers. Aviators donned milkweed-lined flying suits in case their plane crashed into the ocean too. Incredibly, twenty-six ounces of fluff could keep a 150-pound man afloat for up to 48 hours. The Department of Agriculture rallied support for the troops with the slogan, “pick a weed, save a life.”

The milkweed (Asclepias siraca) splits seeds with white fluff at the end of maturation.

Plant a Weed, Save a Life 

Milkweed has served the human population with its myriad benefits—both medicinally and aesthetically. Now, it is time we express our gratitude by protecting the 100+ milkweed species across the Americas and planting milkweeds where they will thrive. The common milkweed (Asclepias syriaca L.) alone, is a vital food source for more than 450 different insects—its vibrant flowers attracting flies, beetles, ants, bees, wasps and butterflies. But among all species that crawl and fly, the monarch butterfly depends on the milkweed the most. And now, with the migratory monarch classified as Endangered by the International Union for Conservation of Nature (IUCN), it is more important than ever before to secure their habitat.

Weighing less than half a gram, these delicate creatures travel nearly three thousand miles from the northern US and southern Canada to their overwintering destination in the oyamel fir forests of central Mexico. Because their life span is limited to just 4-8 weeks, time is precious. Monarchs become sexually mature in February and March, laying eggs on milkweeds as they return north. A female lays 100‒300 eggs during her lifetime. The eggs hatch three‒five days after they are laid. Monarch larvae, or caterpillars, feed exclusively on milkweed leaves. As they feed, they store the cardenolides in their tissue, making them unpalatable. The caterpillars grow and molt several times over a two-week period before forming a chrysalis. The milkweed toxins remain in their system even after metamorphosis. Two weeks later, they emerge with two pairs of fiery orange-red wings, fragmented by black veins and white spots.

Monarch caterpillars and butterflies advertise their noxious nature through a biological mechanism known as aposematism. Their patterns and contrasting colors signal potential predators, like birds, that they are dangerous to eat and thus, should be avoided at all costs. Unbeknownst to the birds, northern monarchs that feed on common milkweed absorb relatively small doses of the toxic compounds, while the more southern butterflies accumulate large amounts of the compounds from other milkweed species and are in fact inedible. This phenomenon is best described by life science writer, Tim Vernimmen:

“They can tolerate this food source because of a mutation in a crucial protein in their bodies, a sodium pump, that the cardenolide toxins usually interfere with. All animals have this pump. It’s essential for physiological recovery after heart muscle cells contract or nerve cells fire—events that are triggered when sodium floods into the cells, causing an electrical discharge. After the firing and contracting are done, the cells must clean up, and so they turn on their sodium pumps and expel the sodium. This restores the electrical balance and resets the cell to its usual state, ready again for action. Cardenolides are noxious because they bind to key parts of these pumps and prevent them from doing their job. This makes animal hearts beat stronger and stronger, often ending in cardiac arrest.”

monarch butterfly on orange milkweed flower

Causes of Butterfly Decline

According to World Wildlife Fund reports, the eastern migratory monarch population shrunk by more than 80 percent during the last three decades. Their decline can be attributed to the degradation and loss of breeding and migratory habitat and overwintering habitat; climate change and the associated increases in severe weather events; pesticides including herbicides, insecticides and fungicides; aggressive management of roadside vegetation through mowing and herbicide spraying; urban development; unsustainable landscaping practices; logging; and loss of grasslands and croplands. Among these threats, milkweed depletion could be the most catastrophic. Milkweed along the butterflies’ migratory route is essential for the species’ survival.

Fortunately, one of the easiest ways to conserve monarchs is by planting milkweed. Milkweeds are resilient plants and can grow almost anywhere—from roadside ditches and prairies—to woodland margins and marshes. There are several dozen species native to North America, so no matter where you live, there is at least one milkweed species naturally found in your area.

Closeup pink milkweed plant flowers green leaf background

Flying Into the Future

“It is difficult to watch monarch butterflies and their extraordinary migration teeter on the edge of collapse, but there are signs of hope. So many people and organizations have come together to try and protect this butterfly and its habitats. From planting native milkweed and reducing pesticide use to supporting the protection of overwintering sites and contributing to community science, we all have a role to play in making sure this iconic insect makes a full recovery,” said Anna Walker, member of the IUCN SSC Butterfly and Moth Specialist Group.

To protect overwintering grounds in Mexico’s Monarch Butterfly Biosphere Reserve, WWF works with the Mexican government, local communities and other partners to promote scientific monitoring, sustainable forest management and education on the monarch butterfly migration.  WWF’s travel partner, Natural Habitat Adventures, is engaged in a number of philanthropic initiatives including: awarding two qualified environmental educators with the opportunity to journey with us on our Kingdom of the Monarchs adventure, funding the restoration of a historic mural in the small mountain hamlet of Angangueo and participating in a cultural exchange during a visit to a local school. Guests get a chance to practice Spanish in the classroom as the students practice their English. Just as the monarchs migrate between countries, this interaction sparks a migration of ideas in younger generations on how to protect this beloved butterfly.

This past winter, WWF Mexico reported a 35 percent increase in butterfly numbers from the previous year. Nat Hab’s Chief Sustainability Officer and Expedition Leader, Court Whelan, expresses how significant this sign of recovery truly is:

A large chunk of my life’s work is raising awareness and advocacy on behalf of the monarch. To me, the IUCN listing is actually encouraging, as it could very well be a key turning point in the fight for monarch conservation. Looking at this as a moment for despair only deepens the trench that monarchs (and other wildlife, for that matter) find themselves in.

Species recovery doesn’t just happen automatically. It occurs because of advocacy and conservation work promoted by people just like you. Small-scale support turns into wide-level support, which influences policy, facilitates new research initiatives, and invigorates programs to plant native milkweed and save monarch habitats on a broad scale. Deeper understanding about what monarchs need to thrive turns into fruitful innovation, such as efforts to pay landowners in both the U.S. and Mexico to conserve monarch habitat. I’m proud to say conservation travel has played a pivotal role in improving the monarch’s fate, particularly in the Monarch Biosphere Reserves in Mexico, by adding tremendous economic value to their winter home deep in the Sierra Madre mountains.

Next time you see a monarch butterfly, look at it not just as an example of natural beauty in our world, but as a symbol for conservation, resilience and hope. And to see millions of monarchs at once, join us in Mexico this winter!