Every Yard Can Be a Rest Stop: The Monarch Migration Through the Shenandoah Valley
Monarch butterflies regularly travel through our area on their way to Mexico, and you can help provide a safe and healthy place for them to stop and rest along the way.
Every fall, something quiet and improbable passes through the Shenandoah Valley.
Monarch butterflies drift south on cold fronts at speeds of ten to thirty miles per hour, covering up to eighty miles in a day on their way to overwintering forests in Mexico. They fly through the Valley, over the Blue Ridge, and through the piedmont east of it, traveling a journey of up to three thousand miles. It’s a journey that successive generations of the butterflies make every single year.
What Makes the Valley Part of the Journey
Monarchs on the eastern migration route move through Virginia in fall following cold fronts south and southwest toward the Gulf Coast. The peak window for Virginia is from early September to late October, with the specific peak in central Virginia and the Shenandoah region falling in mid-to-late September. They don’t fly at night; when darkness comes, they gather to roost in trees, sometimes in numbers large enough to be noticeable if you know what you’re looking at.
The Shenandoah Valley sits along a natural funnel. The Blue Ridge to the east channels southbound migrants along its spine, and Shenandoah National Park’s Big Meadows area has been documented as a site where monarch caterpillars can be found feeding on milkweed in September, before the last generation of the year completes its metamorphosis and begins the southward migration. The caterpillars in that last generation are the ones that will make the full trip to Mexico; a distance and a feat that none of their parents or grandparents accomplished.
The Status Update
The news on monarchs has been complicated over the past few years. In 2022, the International Union for Conservation of Nature designated the eastern monarch as endangered on its Red List, and that classification drew significant attention.
In 2023, following a challenge from biologists who argued the population models were flawed, the IUCN revised that designation to “vulnerable”. Critics argued the the models hadn’t properly accounted for the fact that abnormally high monarch populations in the twentieth century were partly a product of large-scale agricultural land clearing in the 1800s, which created far more milkweed habitat than would have existed historically. When that land reverted to forest, milkweed habitat declined, and so did monarchs.
The habitat is disappearing, and although Milkweed is scarcer than it was two decades ago, the population has been stable since roughly 2014 at levels that are well below historical peaks. The picture is more nuanced than either “endangered” or “doing great.” What is clear is that the loss of milkweed in agricultural settings and along roadsides, through herbicide use and mowing, is a documented and ongoing problem, and it’s one that individual landowners and gardeners can actually do something about.
What the Waystation Program Is
Monarch Watch, a University of Kansas-based research and conservation organization, launched its Monarch Waystation program in 2005 in response to declining populations. The concept is straightforward: create certified monarch habitat in school grounds, church lots, residential yards, community gardens, and municipal landscapes — basically any patch of ground where milkweed and nectar plants can be established and maintained. The “waystation” name comes from the historical idea of a rest and resupply stop along a long route, the same function these habitat patches serve for migrating monarchs fueling up for the next leg of the journey.
Certification requires planting at least ten milkweed plants representing at least two species, along with nectar plants that bloom in spring, summer, and fall, registering the site with Monarch Watch, and committing to maintaining it. There’s a small fee for the official certification and signage, but the habitat itself can be established for the cost of seeds or transplants.
What to Plant in the Shenandoah Valley
Three milkweed species native to Virginia are the standard recommendation for the region. Common milkweed (Asclepias syriaca) is the most widespread and the one monarch caterpillars rely on most heavily across the Valley; it spreads readily and handles Valley soils well. Swamp milkweed (Asclepias incarnata) works in wetter areas and road edges and produces clusters of pink flowers through summer. Butterfly weed (Asclepias tuberosa) is drought-tolerant, blooms orange in summer, and is a good choice for dry sites along the Valley’s sandier or well-drained farmland soils.
One species to avoid despite its wide availability is tropical milkweed (Asclepias curassavica), a non-native that stays in bloom through late fall. That extended bloom is actually a problem, and can delay migration by giving monarchs a reason to linger in areas where winter will eventually kill them. Tropical mikweed can harbor a parasite called Ophryocystis elektroscirrha that spreads more readily when plants don’t die back in winter. Virginia entomologist Doug Tallamy and others recommend cutting tropical milkweed to the ground in early fall if you’re growing it, to avoid these issues.
For nectar plants, the goal is a succession of bloom from spring through October. Late-season nectar is especially critical for the migrating generation, since those are the butterflies building fat reserves for the trip to Mexico. Native asters, goldenrod, ironweed, and blazing star all bloom in the Shenandoah Valley’s fall window and are straightforwardly easy to grow from seed or transplant.
Where to Start
The Monarch Watch waystation registration page walks through the certification process and plant requirements. The Virginia Department of Conservation and Recreation maintains a native-plant guidance page specifically for monarch support. Local nurseries in the Valley that specialize in native plants can generally source all three recommended milkweed species, particularly in spring.
The Monarch Watch waystation program and registration are available at monarchwatch.org. Virginia-specific guidance on native milkweed and nectar plants is available from the Virginia Department of Conservation and Recreation.