03/24/2026
https://www.facebook.com/share/p/1b4AoT9eTg/
Minnesota just planted milkw**d 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 milkw**d (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 milkw**d have established over thousands of years. When you plant milkw**d along that corridor, you are restoring the fueling infrastructure of a transcontinental migration.
The scale of milkw**d loss that created the crisis is almost incomprehensible. An estimated 850 million stems of common milkw**d 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 milkw**d that monarchs require as their sole larval host. Before herbicide-resistant crops, milkw**d 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 milkw**d.
The northern lights blaze over this same stretch of Lake Superior some nights. The monarchs pass through in September. The milkw**d will be waiting.
