How Home Gardeners Can Save The Monarch Butterfly

The Monarch Butterfly is in serious trouble and you – all home gardeners – can help save them.

The Monarch butterfly is one of my favorite garden visitors. I can’t count how many times I’ve sat near my zinnias and watched in awe as this beautiful creature sampled the nectar. But this year I’ll probably see fewer Monarchs in my garden, as record heat and drought, wildfires throughout the American Southwest, years of herbicide spraying on Midwest American farms, and massive logging of the Monarch butterfly’s winter habitat in Mexico, have drastically reduced the population of the only plant Monarchs lay their eggs on, Milkweeds (Asclepias).

Monarch butterflies that once covered 50 square acres of forest during their summer layover in central Mexico now occupy fewer than 3 acres, according to the latest census. The numbers of the orange-and-black butterflies have crashed in the two decades since scientists began making a rough count of them.

Mexico’s National Commission of Natural Protected Areas.

Monarch butterflies migrate thousands of miles every year

To understand the complexity of the declining Monarch butterfly population, one needs to know about its migration. Every autumn, millions of monarchs fly south and west from southern Canada and the United States, their ultimate destination being the forests of the central Mexican states of Michoacán and Mexico. There, they spend the winter before the migration cycle begins anew. Unlike birds, the Monarch migration of thousands of miles spans three to four generations. Most adult Monarchs live for roughly one month, but the final generation lives seven to eight months, enough time to complete the final leg of the flight to central Mexico. Learn more about Monarch Butterflies on National Geographic.

Along the way, adult butterflies feed on many different species of nectar-producing plants. But when it comes time to lay her eggs, the female has only one choice – the closest Milkweed plant.

Monarchs depend on Milkweed, which is vanishing

Discovering a close-by milkweed plant wasn’t a problem in years past, as more than 140 species are native to North America and Mexico, and it was abundant around Midwest farmland in the U.S. But with the widespread adoption of herbicide-resistant GMO corn and soybeans, American farmers have increased their herbicide use, killing off large swaths of milkweed in and around their fields.

Research has shown that corn and soy fields were a favorite stop for Monarch butterflies, but with the milkweed gone, so goes their opportunity to lay eggs. Chip Taylor, director of the conservation group Monarch Watch at the University of Kansas, said the Midwest milkweed habitat “is virtually gone. We’ve lost well over 120 million acres, and probably closer to 150 million acres.”

For Monarch larvae, Milkweed is usually their first meal

But Milkweed is also an important food source for monarch larvae. Upon hatching, the caterpillars consume the milkweed as their first meal. It’s not unusual in fact, for multiple young to practically strip the plant bare – zebra-striped monarch caterpillars gorge themselves on the milkweed’s milky alkaloid sap (hence the plant’s name), which makes the caterpillars poisonous, or at least unappetizing to birds.

Milkweed has also been declining due to extreme weather

As if the decimation from herbicides wasn’t enough, milkweed has also been a victim of the drought and extreme heat throughout much of the U.S., as well as frequent wildfires. What’s more, Monarch butterfly eggs, larvae, and pupae favor mild conditions – temperatures that get above 95˚F (35˚C) can be lethal for larvae. 

The butterflies usually fly north across Texas as they migrate from Mexico into the USA, and according to the National Climatic Data Center, 2012 was the hottest year on record in Texas, coming on the heels of the state’s driest year in 2011. That all adds up to a perfect storm of sorts for milkweed populations, Monarch larvae, and food sources for adult butterflies.

Gardeners can help save Monarch butterflies by planting Milkweed

Gardeners obviously can’t change the weather, but what we can do is offer local habitat to the Monarchs by planting milkweed in our gardens. If you discover a milkweed seedling in your flower or vegetable beds – congratulations, you have free milkweed! – let it grow in that spot, or carefully transfer it to a place better suited.

If you purchase milkweed, it’s important to select a species that’s native to your area. Monarch butterflies are more likely to use varieties that are common to the region and native plants are best adapted to survive local drought, heat, and whatever else mother nature throws at it. You can find varieties native to your area at Wildflower.org’s native plant database. The link will show you the full list of milkweed – narrow your search by your state with the box on the right side of the page.

Milkweed will grow just about anywhere and can be started from seed or rhizome cuttings. These will usually bloom in their second year. Plants bought from your local nursery should bloom this year, between May and August. Milkweed can be invasive, however. Plant it in an out of the way, semi-dry place where it won’t present problems for your other plants.

The danger to the Monarch butterfly population is that the smaller the colonies become, the more vulnerable they are. “The severe drought in Texas and much of the Southwest continues to wreak havoc with the number of monarchs,” says butterfly tracker Craig Wilson, a senior research associate at Texas A&M University. “It takes four generations of the insects to make it all of the way up to Canada, and because of lack of milkweed along the way, a lot of them just don’t make it.”