Landscape plant selection and management for slope restoration on urban freeways

MSU researcher Bert Cregg worked to improve the success of roadside plantings in urban areas.

Researcher: Bert Cregg
Awarded: $39,500
Leveraged: $613,476

Establishing landscape plants such as shrubs, herbaceous perennials and ornamental grasses can increase the diversity of highway roadside plantings. Bert Cregg, a professor in the MSU departments of Horticulture and Forestry, sought to increase the plant diversity along I-696 near Warren, Michigan, and Roseville, Michigan.

Landscape plantings along roadsides provide a range of benefits, including slope stabilization, improved aesthetics, increased biodiversity, reduced need for mowing, and improved driver awareness and safety. However, highway roadsides are difficult sites on which to establish plants, particularly on sloped roadsides in urban areas. Plants on these sites are often subjected to poor soil conditions such as alkaline soils, low organic matter and loss of soil structure due to site disturbance during construction.

Roadside plants also face aboveground stresses, including elevated temperatures associated with urban heat island effects and increased wind exposure due to nearby traffic and wind tunnelling effects of sloped freeways. As a result, initial plant establishment of urban freeway plantings is often poor, and large-scale planting failures can occur.

Cregg and his team undertook this research project with the long-term goal of improving the success of roadside plantings in urban areas. They examined the effects of site preparation and plant selection on plant establishment, as these are two key drivers of plant survival and growth and are factors over which roadside managers have control. The team found that adding compost to roadside soils greatly increased plants establishment, and they developed a roadside plant selector tool to help roadside managers to identify plants that are well-suited for challenging roadside environments.

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