Mowing the state highway rights of way is in full swing after the wet spring delayed Minnesota Department of Transportation maintenance workers from starting the job earlier. MnDOT crews mow approximately 45,000 acres of land annually.
MnDOT, like other landowners in the state, is required to control plants on the Department of Agriculture’s restricted noxious weed list. Mowing is one way MnDOT controls them. Many of the plants seen along roadsides display vibrant colors when in bloom, but to the trained eyes of MnDOT’s roadside vegetation crews, they are invasive and a threat to native plants, animals and ecosystems.
“We want a diverse plant population on our roadsides because it’s healthier to have different kinds of plants and grasses,” Tina Markeson, roadside vegetation supervisor, said in a release. “When invasive species take over, it causes issues in the long run.”
Markeson cited purple loosestrife as an example of an invasive plant that competes with native species. The invasive plant can form dense stands that replace native plants needed by wildlife for food and habitat, she said.
Mowing is usually limited to shoulders and medians to:
- Maintain sight distances for crossing and merging traffic
- Allow motorists to see approaching wildlife
- Aid in the identification of erosion issues
- Allow people to exit the vehicle if needed
State law restricts mowing the entire right of way until after July 31 to protect ground nesting birds.
Timing of the mowing is important to prevent seed formation and so plants are not moved down the road in mowing equipment.
“We aim to mow when plants are in their bud stage, so we’re not spreading the seeds and making the problem worse,” Markeson said. “Knowing the weed and the timing of its development saves money so the right method or combination of methods is used at the right time.”
Some of MnDOT’s mowers have automated vehicle location systems to help maintenance crews mow around noxious weed patches. Operators use an on-screen map to mark new areas of noxious weeds and go back at the right time to mow or spray. The technology also tracks the use of herbicides, when used, so operators can better track where areas are sprayed. The technology is anticipated to reduce herbicide usage by 50 percent.
MnDOT also uses prescribed burns and biological controls to control weeds.
“MnDOT’s goal is to provide a roadside environment that is ecologically appropriate and self-sustaining and maintains scenic qualities, while ensuring traveler safety,” Markeson said.
For more information, go to MnDOT’s roadside vegetation management program website, www.mndot.gov/roadsides/vegetation/.
