How to Spot Migrating Monarch Butterflies in Tennessee

Most of us would undoubtedly picture a monarch if asked to imagine a butterfly, recognized by their vivid orange wings veined with black and known for their incredibly long migration patterns. While the majority of these beautiful butterflies spend their summers in the Northern United States and Southern Canada, they do traverse the Volunteer State on their journey, arriving in early April and departing in mid-September. Grab your binoculars and camera as we zoom in on Tennessee’s monarch migration.

Where Do Monarch Butterflies Migrate?

Though they have an established presence in other parts of the world, the majority of monarch butterflies (Danaus plexippus) spend their lives traversing the North American continent. Because these delicate insects can’t survive in the cold, they migrate from their breeding grounds and summer homes in the Northern U.S. and Southern Canada to warmer climates in colder months.

There are two distinct groups of monarch butterflies in North America, separated by the Rocky Mountains. Those west of the Rockies spend their winters along the California Coast between Santa Cruz and San Diego, and down into the Baja Peninsula of Mexico, while their Eastern cousins migrate to the oyamel fir forests of Central Mexico. Though the Arctic tern (Sterna paradisaea) and gray whale (Eschrichtius robustus) have decisively longer migrations, monarch butterflies hold the record for the longest insect migration.

Why Migration Is a Multi-Generational Affair

The monarch’s migration is a multi-generational affair in which each successive generation plays a crucial role. In late winter, monarchs that have spent the winter in Mexico embark on the initial leg of the trip back North. From Mexico, these intrepid fliers make their way to the southern United States, where they will mate, lay eggs, and die. Some hardy first-generation monarchs make it to Tennessee, typically in early April, but many of the monarchs spotted in the Volunteer State are second generation.

Though most monarchs that emerge in Tennessee continue north, a small portion of eastern monarchs remain in Tennessee throughout the summer. “Not all monarchs go to the Northern U.S. and Canada,” according to Steve McGaffin, Curator of Education and Citizen Science Coordinator at Zoo Knoxville. “Some monarchs will stay in Tennessee, going through multiple generations over the course of the summer,” McGaffin continues. He is also a data producer with the North American Butterfly Monitoring Network. “Think of it not as everyone flies to the northern U.S., but more as a filling up of the U.S. east of the Rockies, where most will continue north, but many won’t,” he says.

Why Milkweed Is Important for Monarch Butterflies

Beginning in early April and throughout the spring, monarchs will be traveling across the state, though they might be too high to notice. Migrating monarch butterflies typically fly from 800-1,200 feet high, though there are verified sightings of these amazing creatures flying as high as 13,000 feet!

The timing of their arrival optimally coincides with the emergence of milkweed, which is essential to the monarch’s survival. Milkweed (Asclepias) is the only plant on which monarch butterflies will deposit eggs, and from which their larvae will feed.

“Milkweed is important,” according to McGaffin, “but it is just as important to have a variety of native nectar plants that bloom across the flight season to feed the adult monarchs and other butterflies.” He suggests having at least three native wildflowers for each season—spring, summer, and fall. “This means you should plan to have at least nine different species of native wildflowers in your yard, including milkweed,” he says. McGaffin further cautions against the use of pesticides and patronizing nurseries that pretreat their plants with these chemicals, which can kill butterflies.

The best way to view monarchs in Tennessee is to create a welcoming environment for them. Filling your yard with a variety of seasonal native wildflowers, as McGaffin advises, or creating a community butterfly garden are two excellent ways to witness monarchs in the Volunteer State while also supporting their survival. Though not yet officially considered an endangered species, monarch butterflies are experiencing an unprecedented population decline as a result of habitat destruction, exposure to pesticides, and climate change.

When to See the Monarch Butterfly Super Generation in Tennessee

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The true magic of monarch migration occurs in late summer when these butterflies journey south. The final generation to emerge in late summer is considered a super generation that is capable of traveling the entire 3,000-mile distance to Mexico. This super generation lives up to eight times longer than preceding generations, thanks to diapause, a physiological condition in which their metabolism slows significantly and their reproductive development is suspended.

The super generation can be seen in the Volunteer State between mid-September and mid-October most years. Under ideal conditions, there will be more monarchs crossing the state in the fall, according to McGaffin. “There are a lot of variables that affect the fall numbers,” he explains. “If the northward migration went well and conditions—including weather, milkweed resources, and nectar resources—were good, then we would expect the fall numbers to be higher,” he says. “But if the northward migration was difficult, and/or conditions were poor during the summer, then the fall migration numbers could actually be lower, and overwintering numbers will be low in Mexico.”

While spring and fall provide opportunities for Tennesseans to view monarchs in migration, if you’re invested in seeing monarch butterflies in Tennessee, your best bet is to plant a garden that will attract them. Even if monarchs do not appear, you’ll still have a beautiful garden.

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