Planting the seed for native species on Illinois roadsides

Planting the seed for native species on Illinois roadsides

Roads and highways serve as more than just a way to move people and goods - they also hold the potential to host native plant species, providing environmental and economic benefits. A joint project led by IDOT Roadside Maintenance Manager Scott Hall with the Illinois Center for Transportation at the University of Illinois Urbana-Champaign aims to evaluate the use of native species on Illinois roadsides.

"The use of native vegetation along roadsides is important because native vegetation is a sustainable, low-maintenance solution that helps to stabilize soil and reduces erosion, helps to filter runoff and improve water quality, and provides crucial habitat for pollinators," Hall said. "This vegetation helps to reduce maintenance costs, herbicide use, creates natural beauty, and can act as safety barriers by reducing snow drifts. This study identified the most suitable native vegetation to utilize on Illinois roadsides as well as reexamine the types of vegetation we currently have in our standard seed mixes."

Using native species comes with challenges, however, as IDOT has historically planted mostly non-native species on roadsides. Little research has been conducted on which native species will grow and thrive. 

"The goal with roadside planting is not necessarily to restore a native prairie, but to plant native species that provide certain benefits that the native species provide," said UI Professor Jeffrey Matthews. "The rationale behind our work was to determine which [native] species are more or less appropriate for planting on roadsides."

The researchers examined 34 existing roadside plantings in Illinois and Indiana to see what native species were present, learn how they were maintained and determine factors that may have led to their long-term success. Factors that may contribute to successful planting include distance from the road, soil compaction, surrounding land uses and soil conditions, among others. 

They also designed and planted native mixes at four IDOT locations, doing a side-by-side comparison of existing IDOT seed mixes to their newly designed ones. Newly developed designs with native species, created by UI Graduate Research Assistant Wesley Bollinger, include those for use in roadsides, lawns and sloped areas.

Ultimately, the researchers found that coverage of native species tended to increase farther from the road but decreased in areas with higher levels of soil nitrate and phosphorus. Their results after planting showed that using native species on roadsides in Illinois is a viable, cost-effective practice, provided they are maintained correctly.

"There's a lot of good for the environment to be done with this, but also a lot of good from a dollars and cents perspective within the DOTs themselves," Bollinger said. "There's plenty of evidence to suggest that native species can do well in these areas."