Monarchs and Milkweeds on Highway, Railroad and Electrical Transmission Lines Rights-of-Way


In the U.S. alone, there are more than 17,000,000 acres along federal, state and county highways that can potentially contribute to monarch butterfly recovery. The millions of linear miles of roadside right of ways that are dedicated to native vegetation can serve as potential habitat for monarchs as well as other butterflies, if they are positively managed for milkweeds and other nectar plants. In addition, there are more than 186, 400 linear miles of electrical transmission line rights-of-way along utility corridors in the U.S. Depending how they are managed, these linear corridors of public or private lands can provide up to 9,646,000 acres of potential pollinator and nectar plant habitat in the United States [Wojcik and Buchmann 2012].

Except in a handful of innovativestates such as Iowa [see success stories, below], these habitat corridors have scarcely been managed to provide non-toxic habitat for milkweeds or other nectar and host plants needed by monarch butterflies. However, other states such as Minnesota have passed Reducing Mowing Laws to limit the impacts of roadside mowing on wildlife such as nesting songbirds and gamebirds; these same laws and regulations could also control the negative impact of mowing on monarchs and other butterflies through better timing and reduced frequency of roadside maintenance. Monarch reproduction and migration occur at sonmewhat different times from locality to locality, with the overall “watch period” of heightened concern occurring anywhere from July  to the first week in October. Depending where you are, most eggs of the monarch generation that will migrate are laid between July 25th and September 10th so learn to observe within this window the most critical time for refraining from mowing in your area..

Poorly managed roadside and transmission line right-of-ways can fragment or bisect landscapes into island-like patches too small to support viable populations of threatened plants or animals. They may also be mowed or sprayed at an inappropriate time for the lifecycle of monarchs or for the flowering of milkweeds and other plants. However, the rainwater runoff draining from roadsides into these right-of-ways often creates more abundant plant cover, and enough moisture reaches plant roots to assure their flowering and fruiting. While herbicide spraying of croplands may deplete milkweed and monarch populations on private agricultural lands, the right-of-way for highways and transmission lines can be thoughtfully and capably managed to control exotics, favor milkweeds and other pollinator-attracting plants, and avoid disruptions to the last generation of monarchs before their flight to Mexico or to California.


What You Can Do:

  • Get to know the innovators and conservation-conscious professionals in your federal, state or county highway authority in order to forge collaborations for activities such as collecting the seed of milkweeds and other nectar plants, or propagating such monarch-attracting species in rights-of-way segments where they have been lost or depleted. They can inform you of protiocols and collaborations you can participate in.
  • Work with your state native plant society, local garden clubs or botanical gardens to propagate an increased diversity of native milkweed seeds, and then transplant out their established seedlings in “plugs” to better-watered patches along roadsides or under transmission lines.
  • Work with highway maintenance crew supervisors to eliminate or reduce the impact of mowing or spraying in both natural and transplanted milkweed and other wildflower populations,  reducing the mowed area to the first eight feet off highway pavement, and no lower than a foot from the ground.
  • Encourage highway maintenance supervisors to refrain from any mowing during the peak flowering and fruiting of the nectar, pollen and host plant populations required by monarchs. Cease mowing operations for the period of development for migrating monarchs, which may range from July  7th through late September, depending on the weather in your locality.
  • At all costs, control or eliminate mowing or herbicide spraying of flagged patches of milkweeds where monarch larvae have been found during their later in-star stages, particularly for the final generation of monarchs just before their migration to Mexico or California in late summer.
  • Request that Congress consider a national Reducing Mowing policy as part of the next Transportation Reauthorization Bill that would reconcile the needs of birds, butterflies and bees in mowing protocols for all fifty states, with particular regard for monarch recovery.

Success Stories

At the Tallgrass Prairie Center associated with the University of Northern Iowa, the staff propagated milkweeds and collected nine pounds of seed from them in 2013 for outplanting in Iowa highway roadsides. Through the Integrated Roadside Vegetation Management programs of the state of Iowa and with the guidance of Monarch Joint Venture biologists, the Tallgrass Prairie Center provides seed, technical assistance, training and education to county and state department of transportation staff. Since 1998, 78 counties in Iowa and adjacent states have received Transportation Enhancement seed that has helped restore 10,000 acres of roadside to natural vegetation, which includes milkweeds in many places. Under the direction of Dr. Laura Jackson, the Tallgrass Prairie Center is “setting the table” for the comeback of monarch butterflies, using native milkweeds [Wines 2013]. This model state program has fostered the kind of collaborations to implement tangible solutions on the ground, ones that are now being replicated in other states.

The Iowa-based initiative is niot the only effort at transplanting out “milkweed plugs” to highwaysides and other rights-of-way. In 2013, Monarch Watch had 21,000 plus of milkweeds contract-grown for outplantings in right-of-ways and other public spaces. In 2014, Monarch Watch’s Director Chip Taylor anticipates that at least 45,000 to 60,000 milkweed plugs will be propagated for outplanting, and over one hundred thousand milkweed outplantings in public spaces are possible this next summer if non-profit or corporate spoonsors are recruited to underwrite these efforts. Such roadside plantings have already occurred or are are underway in Arizona, Iowa, Kansas, Minnesotas, Texas and Virginia.


Further Reading and Links:

Harper-Lore, B. and M. Wilson. 2000. Roadside Use of Native Plants. Island Press, Washington, D.C.

Hopwood, J. 2010. Pollinators and roadsides: managing roadsides for bees and butterflies. Xerces Society Invertebrate Conservation Guidelines.

Reeder, K.F., D.M. Debinski, and B.J. Danielson. 2005. Factors affecting butterfly uses of filter strips in Midwestern USA. Agriculture, Ecosystems and Environment 109: 40 –47.

Wines, Michael. 2013. Setting the table for a regal butterfly comeback, with milkweed. New York Times, December 20:1.

Wojcik, V.A. and S. Buchmann. 2012. Pollinator conservation on electrical transmission and roadside rights-of-way. Journal of Pollination Ecology 7 [3]: 16-26.


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