Safe, Sustainable Roadside Mowing

by Amanda Bancroft

Land management is a lot like cooking. You have to get the timing and ingredients just right, or it’s a disaster. To boost a prairie’s health, for example, controlled burns can be part of good management practices.

“If you want more grasses, do a spring burn; for more wildflowers, do a fall burn,” said Joe Woolbright, prairie restoration specialist.

Timing is incredibly important when managing roadsides. Both the season and frequency of mowing have ecological consequences. According to the Xerces Society’s guidelines for managing roadsides for bees and butterflies, “Roadsides in the U.S. cover more than ten million acres of land.” This yields a treasure for local wildlife and pollinators. “Pollinator habitat along roadsides supports the pollination needs of adjacent farms and natural areas.” This in turn boosts not only native diversity of flora and fauna, but also the local agriculture economy, such as honey production.

When roads are mowed carelessly in the spring, before wildflowers have had a chance to go to seed, it prevents their ability to thrive the following year and hinders their ability to sustain our native pollinator population. Carefully incorporating a diversity of native plants not only helps pollinators but also promotes motorist safety, reduces maintenance costs, and improves roadside aesthetics, boosting tourism and enhancing our state’s natural beauty. Native plants along roadsides offer a historical perspective, too, recreating the way our local prairies once looked.

How do they do all that?

Native grasses and wildflowers are specially adapted to our local conditions, making them better than non-natives in tolerating drought or heat. Natives reduce the need to use herbicides and may provide erosion control from their strong root development. Natives are less likely to spread into rights-of-way, meaning that it’s cheaper to manage them than it would be to continuously mow or spray invasive non-natives.

But is it safe to just leave the wildflowers?

Mowing a narrow strip along the shoulder and determining the least damaging times to mow are a good place to start. “Mowing roadside vegetation generally has three aims: to improve driver visibility, to provide room for a vehicle to pull off the road if needed, and to prevent encroachment of brush or trees. There is no need to mow the entire roadside to achieve these objectives,” notes the Xerces Society.

In the Midwest, mowing once a year in July promoted wildflower growth, but limited the fall growth of asters and sunflowers which certain bees depend on. Minnesota regularly mows eight feet from the shoulder but the entire right-of-way may only be mown after August first. This protects nesting birds.

A well-researched plan is better than one based on assumptions. We might assume deer are more likely to be drawn to roads with unmowed tall grasses. Surprise! Deer prefer tender new growth, which is exactly the kind of diet that frequent roadside mowing creates, encouraging more deer to jump out in front of vehicles and causing accidents.

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