University of Minnesota

Monarchs and Permits for Roadside Mowing in Minnesota

Posted on Monday, January 30, 2017 at 2:21 pm in Monarch Conservation Efforts, Monarch Lab Research Updates

(Photo: Monarch Lab)

A recent study from the U of MN Monarch Lab (Kasten et. al, 2016) shows that roadsides, if managed appropriately, have the potential to be productive breeding habitat for monarchs. Monarchs need milkweed to reproduce and feed on as caterpillars, and development and changing land use has removed a lot of milkweed and native nectar plants from the landscape, especially in agricultural areas. Roadside rights-of-way provide an exciting opportunity for pollinator habitat because they make up a large area of undeveloped land in a rapidly changing landscape.

In this study, roadside sites were monitored for milkweed and immature monarch density during the summer of 2015 in a 250 mile radius from Minneapolis, reaching from Minnesota into Wisconsin, Iowa, and South Dakota. This research found milkweed in 60% of all surveyed roadsides. Immature monarchs were found every week from July 13th to September 9th, and during these weeks immature monarchs were found at 23.5% of sites containing milkweed (Kasten et. al, 2016).

We are optimistic about the habitat potential of roadsides, especially due to the fact that monarch density at sites with milkweed was higher at sites that were adjacent to unsuitable monarch habitat such as forest and corn or soy fields (Kasten et. al., 2016). This implies that monarchs are more likely to use roadside habitat when there is not other suitable habitat nearby. Roadsides also have the potential to provide important connectivity in currently fragmented monarch habitat, if managed appropriately.

Threats facing monarchs on roadside habitat include untimely mowing, pesticide application, the presence of heavy metals and salts, and vehicle mortality. Proper management practices such as well-timed mowing and the planting of native nectar plants may be able to mitigate some of these threats.

A bill related to roadside right-of-way mowing has been introduced in the Minnesota Legislature. House File 124 and Senate File 218 would prohibit Minnesota roadside authorities from requiring permits for roadside mowing or haying, and could result in increased roadside mowing. The Minnesota Department of Transportation has historically required permits for individuals to conduct activities such as mowing or research on rights-of-way. An updated mowing permit was announced by MNDOT last year, which has led to much debate on this topic.

Existing state law prohibits mowing of roadsides prior to August 1st in order to protect habitat for grass nesting birds such as pheasants, quail and song birds (Minnesota Statute 160.232). The Monarch Joint Venture used MLMP and Monarch Watch data to create regional mowing guidelines in order to protect milkweed and nectar habitat until monarchs have migrated out of a region. The MJV handout suggests that mowing is least detrimental to monarchs in North and Central Minnesota after September 30th and Southern Minnesota after October 1st (Monarch Joint Venture).

To find out more information about mowing permitting visit MNDOT’s mowing webpage.  If you wish to contact your state representative regarding this bill or roadside pollinator habitat visit the Minnesota State Legislature website.



Kasten, K., Stenoien, C., Caldwell, W., Oberhauser, K S.  2016. Can roadside habitat lead monarchs on a route to recovery? Journal of Insect Conservation doi:10.1007/s10841-016-9938-y

Minnesota Statute 160.232. MOWING DITCHES OUTSIDE CITIES. Office of the Revisor of State Statutes, 2016.

Monarch Joint Venture, 2016. Mowing: Best Practices for Monarchs.


Header photo shows roadside monitoring during the summer of 2015. Photo by Monarch Lab staff.

  • © 2018 Regents of the University of Minnesota. All rights reserved.
  • The University of Minnesota is an equal opportunity educator and employer. Privacy