Establishing persistent plant growth along roadsides is challenging in cold climates like Minnesota’s. Besides the poor soil conditions often found along roadsides, these areas are subject to snowplow damage, extremes in weather, exposure to deicing salt, and scant maintenance. The resulting sparse vegetation cover leads to more soil erosion and greater likelihood that invasive weeds will move in.
In a multi-phase study spanning nearly 10 years, U of M researchers partnered with the Minnesota Department of Transportation (MnDOT) and four other northern universities to develop recommendations for turfgrass seed mixtures that would improve the health of roadsides and save resources for local communities. In addition, the research team sought input from other state departments of transportation, local governments, and industry to inform their recommendations. Their work was honored with CTS's 2025 Robert C. Johns Research Partnership Award.
Led by Eric Watkins, professor in the U of M’s Department of Horticultural Science, researchers first evaluated 60 different grass varieties by establishing on-site trials in Michigan, Minnesota, Nebraska, New Jersey, and Wisconsin. Results of that phase identified turfgrass varieties that performed well when subjected to the stresses of heat, ice cover, and salt—and demonstrated the need for locally generated data on how the roadside turfgrass performed.
“Testing at locations in multiple states, using funding from multiple DOTs, resulted in more useful results for us to base future cultivars recommendations on,” Watkins says.
Building on those results, the team developed a series of mixtures of top-performing grasses that were seeded and assessed at 14 roadside sites across Minnesota. Field results showed that increasing the number of species in a mixture resulted in more living turfgrass, fewer weeds, and less bare soil at risk of erosion. The research team determined that MnDOT should consider creating three separate turfgrass roadside mixture recommendations for the state based on location and soil quality.
Including seed vendors in discussions about the feasibility of the team’s recommendations was an important component of the work. “One of the challenges we’ve faced when recommending the most well-adapted turfgrasses for roadsides is that the seed is not always commercially available,” Watkins says. “If we recommend a mixture that is not going to be available for the foreseeable future, then our work will not have any impact, and MnDOT will be left approving a series of substitutions, few of which are backed by solid research.”
In addition, the testing sites allowed the team to interact with public landscape managers from every corner of the state. “Conversations with these stakeholders showed us the challenges they face with timelines, equipment availability, labor, and the diversity of tasks they are responsible for.”
With data from MnDOT, the team also developed a budget tool to help public agencies make informed roadside seeding decisions. The researchers are now taking advantage of the existing field sites to collect longer-term data throughout multiple growing seasons.
Based on the team’s recommendation, MnDOT has also implemented a change in its processes to allow for updating turfgrass seed and sod mixture recommendations annually, allowing stakeholders to use the newest genetics available on the market—a new model that Watkins expects other agencies across the nation to follow.
“Establishing turfgrass that serves all functions will always be complicated,” says Dwayne Stenlund, erosion control specialist with MnDOT and a member of the research team. “But as a vegetation tool to solve establishment and persistence problems—especially in urban areas where native plants are not feasible—these species alternatives and flexibility will greatly help with turfgrass requirements in many areas.”
The Research Partnership Award is named in honor of former CTS director Robert Johns. The award is presented annually to a team of individuals who have collaboratively drawn on their diverse expertise to achieve significant impacts on transportation.
Project team
- University of Minnesota: Eric Watkins, Chengyan Yue, Jon Trappe, Kristine Moncada, Dominic Christensen, Andrew Hollman, Joshua Friell, Sam Bauer
- MnDOT: Dwayne Stenlund, Kenneth Graeve, Warren Tuel
- University of Wisconsin: Mark Renz, Doug Soldat
- Rutgers University: James Murphy
- Michigan State University: Kevin Frank
- University of Nebraska: Bill Kreuser
—Amy Friebe, CTS senior editorial manager
