03/24/2026
https://www.facebook.com/share/p/1b4AoT9eTg/
Minnesota just planted milkweed fields along the most important butterfly highway in North America. The sign in the photograph is not metaphorical. Interstate 35 is officially, legally designated the Monarch Highway — and the state just started treating it like one.
In June 2025, the Minnesota Department of Transportation planted milkweed (Asclepias syriaca and Asclepias incarnata) at the Thompson Hill Rest Area overlooking Duluth and Lake Superior on I-35. The site was chosen with precision: it sits at the northern terminus of the monarch's breeding range migration route, the point where northward-migrating monarchs in late spring reach the boreal forest edge and turn around to begin the southern migration that will take them — through successive generations — back to Michoacán, Mexico by November.
The Monarch Highway designation of I-35 reflects a biological reality that has existed for millennia. The corridor runs 1,568 miles from Laredo, Texas at the Mexican border to Duluth, Minnesota at the western tip of Lake Superior — tracing almost exactly the western edge of the tallgrass prairie biome where monarch breeding populations have historically been most dense. Monarchs don't follow roads. But I-35 happens to parallel the migratory pathway that geography, prevailing winds, and the distribution of milkweed have established over thousands of years. When you plant milkweed along that corridor, you are restoring the fueling infrastructure of a transcontinental migration.
The scale of milkweed loss that created the crisis is almost incomprehensible. An estimated 850 million stems of common milkweed were eliminated from the Midwest agricultural landscape between 1999 and 2014 — the direct result of herbicide-resistant corn and soybean varieties that allow farmers to spray entire fields with glyphosate, killing every non-crop plant including the milkweed that monarchs require as their sole larval host. Before herbicide-resistant crops, milkweed grew at field edges, in drainage ditches, along fence rows — a distributed, resilient network across 70 million acres of farmland. That network is now largely gone. What's left are highway rights-of-way, parks, and the yards of people who choose to plant it.
Duluth is the right place for this. The city sits on a geological funnel: the western tip of Lake Superior forces migrating birds and insects to compress into a narrow corridor before they can continue south, creating one of the most spectacular migration concentration points in North America. Hawk Ridge Bird Observatory documents 90,000+ migrating raptors annually at Duluth. Now the monarch waystation at the threshold of that funnel has milkweed.
The northern lights blaze over this same stretch of Lake Superior some nights. The monarchs pass through in September. The milkweed will be waiting.
