The success of wildflowers seeded in roadside ditches hinges on neighboring land types, according to the findings of a recent study conducted by University of Nebraska–Lincoln researchers and the Nebraska Department of Transportation.
Focused on roadside plantings across the Cornhusker State, the study was conducted to gauge the success of Nebraska’s practice of using native mixtures of grasses and wildflowers as vegetation in ditches. The planting mixes are developed to prevent erosion and increase visual aesthetics of roadside ditches.
While the wildflowers may be more visually appealing, the challenge is that they often fail to establish and persist as long as grasses, said Walt Schacht, Sunkist Fiesta Bowl Professor of Agronomy.
“Across the state, we located 10-12 sites that had been seeded at least 10 years ago to see what grasses and what wildflowers persisted,” Schacht said.
The research was led through a collaboration of the Department of Agronomy and Horticulture’s range, forage and pastures group; Jon Soper and Carol Weinhold of the Nebraska Department of Transportation; and E.J. Raynor, a postdoctoral research associate.
The study found that neighboring land types — such as rangeland or cropland — dictate the success of roadside revegetation in providing diverse and native plant communities.
In the cropland-dominated eastern regions of Nebraska, roadsides experienced 20-30% fewer native species that established from nearby seed sources than roadsides in the rangeland-dominated Sandhills and Panhandle. Additionally, a roadside site in central Nebraska, which was surrounded by rangeland, supported almost twice as many species as a nearby cropland-surrounded roadside.
Overall, the number of plant species detected at Sandhills’ roadsides as well as Panhandle locations was at least 15 species greater than roadsides in central and eastern Nebraska. This result suggests that the level of management necessary on western Nebraska roadsides is less than that on eastern locations with high exposure to non-native seed sources.
A Floristic Quality Assessment of roadsides in the northeast revealed high production of seeded native grasses, such as eastern gamagrass and switchgrass, increased the ability of revegetation efforts for restoring native-plant dominance in a region of the state highly invaded by non-native grasses, such as smooth bromegrass. Sites with low levels of the native grasses were dominated by communities of lower conservation value and high non-seeded, non-native grass composition.
“This foundational work on Nebraska roadside plant community ecology establishes that Nebraska roadsides are viewed as a resource where plant communities with a diversity of native grassland species can be established,” Schacht said. “However, the persistence of many seeded, native species is minimal because of the competitiveness of both seeded and invasive species of grass.”
With the findings from this study, the Nebraska Department of Transportation has continued to evaluate and modify its roadside seeding mixtures. Additional collaborations have formed focused on increasing persistence of wildflowers on Nebraska roadsides.
A summary of the research was recently published in Environmental Management.