On the road again: Using native plants in lieu of non-native turfgrasses on midwestern highway roadsides

Bollinger, Wesley John

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https://hdl.handle.net/2142/129973 Copy

Description

Title

On the road again: Using native plants in lieu of non-native turfgrasses on midwestern highway roadsides

Author(s)

Bollinger, Wesley John

Issue Date

2025-07-25

Director of Research (if dissertation) or Advisor (if thesis)

• Matthews, Jeffrey
• Bhattarai, Rabin

Department of Study

Natural Res & Env Sci

Discipline

Natural Res & Env Sciences

Degree Granting Institution

University of Illinois Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Prairie
• grassland
• restoration
• transportation
• seed
• ecology
• highway
• habitat

Abstract

To provide evidence-based improvements to Departments of Transportation (DOTs) roadside seeding methodologies and improve results for restoration practitioners working near roadways, I conducted several projects to evaluate processes for increasing native species richness and cover on highway roadsides while reducing invasive species cover and richness. These projects were a literature review of the benefits and existing best-practices for native seeding on roadsides, a review of Midwestern Department of Transportation (MW DOT) specifications manuals usage of native species, an experimental planting of native mixes compared to existing Illinois Department of Transportation (IDOT) mixes, and a survey of previously planted roadsides across Illinois and Indiana. The review of MW DOT manuals showed that Minnesota DOT (MnDOT) specifies 108 species across 11 mixes with detailed establishment and maintenance specifications, the most of any MW DOT. Michigan DOT (MDOT) does not list any native species for roadside seeding. Indiana DOT (InDOT) lists a single native mix used for floodplain seeding that contains few wet soil tolerant species, and Missouri DOT (MoDOT) lists native species but no mixes for their use. All other MW state DOTs reviewed (Illinois, Iowa, Ohio, Wisconsin) list multiple native mixes and between 22 and 75 native species. Different MW DOTs list notable techniques for establishing native vegetation including the use of native prairie straw hay for mulch, use of a hydroseeding unit, and snow seeding in mid-late winter, along with using local ecotype seeds. Generally, MnDOT contains the most complete best-practices for native species establishment and their specifications should serve as a template for other DOTs. I designed new native seed mixes and field tested these mixes in comparison with existing IDOT mixes. After one year of growth in lawn, roadside, and slope areas, I found overall positive effects on native species cover using the newly designed native mixes, including higher native richness for all experiments, and higher native cover for all but one experiment. Eleven of the 39 seeded native species in these trials established in more than half of their seeded plots and thus have value for year one germination and cover in seed mixes. This project shows that native species can be viable as inclusions in —or direct replacements to— several IDOT nonnative mixes, and their first-year success can be improved with alterations to seeding technique. I surveyed 34 native species plantings along roadsides in Indiana and Illinois and evaluated several variables to determine which factors led to long-term establishment. Here I found that high cover and richness of seeded native species and all native species is generally increased with greater distance from road, proximity to surrounding developed land, greater seed mix diversity and decreased soil nitrate and phosphorous. I found that introduced (non-native, non-seeded) species cover increased with fewer species in the seed mix and higher soil fertility, salts, and calcium. Introduced species richness increased with higher proximity to development, proximity to the road edge and higher soil organic matter, phosphorus, and potassium. Across all sites, 84 of the 150 native species seeded at sites were never observed in my surveys, but 28 native species were observed at more than half of the sites in which they were seeded, signaling their value in native roadside plantings. This may signal that other seeded native species do not persist on roadsides, although data on most wetland-tolerant native seeded species were limited in this project due to a low number of surveyed wetland mixes. Without data on maintenance records from these sites, it is hard to predict how habitat management has affected long-term persistence and establishment of these plantings. However, I believe maintenance mowing or prescribed burns likely have a significant impact on overall planting performance due to the pronounced impact of the random effect of site on model fit. My results suggest that native plantings can persist on roadsides for several years after planting but that specific site-level factors increase the likelihood of long-term success. Overall recommendations to DOTs and roadside managers include a list of most observationally and experimentally successful native species grown from seed for use in roadside planting. I advocate seeding into nutrient poor, basic, low soluble salt soils, seeding diverse mixes, and seeding a more diverse mix at greater than 4 meters distance from the road. I also advocate use of a hydroseeding unit or rangeland seed drill for seeding, and several maintenance mows in the first two years’ peak growing season followed by mowing or prescribed burning every 3-5 years afterward per guidelines from MnDOT.

Graduation Semester

2025-08

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/129973

Copyright and License Information

Copyright 2025 Wesley Bollinger

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