Native plants for roadside revegetation in Idaho

Abstract

Establishing perennial plant communities on roadsides is a proactive approach to sustainable road management. The environmental and economic benefits of increasing desirable roadside vegetation include improving slope stabilization, soil conservation, and roadway safety while reducing erosion, maintenance costs, and invasive plants. This study evaluated the success of roadside revegetation on 16 sites in Idaho and on one site in adjacent southwest Montana. Study sites represent a diversity of climatic, topographic, and edaphic conditions in order to provide a variety of examples of roadside revegetation projects in 6 different ecoregions of Idaho. We measured all species’ canopy cover, including noxious weeds and other invasive plants. Of the seeded grass species, 21 of 27 established. Bluebunch wheatgrass (Pseudoroegneria spicata (Pursh) Á. Löve [Poaceae]) and Idaho fescue (Festuca idahoensis Elmer [Poaceae]) were the best-performing native grasses. Seeded grass species that consistently established but had a low mean canopy cover (2–5%) included sheep fescue (Festuca ovina L.), western wheatgrass (Pascopyrum smithii (Rydb.) Á. Löve [Poaceae]), and basin wildrye (Leymus cinereus (Scribn. & Merr.) Á. Löve [Poaceae]). Seeded forbs and shrub species had low establishment success and low mean percent canopy cover. For example, no seeded forb species had more than 1% mean canopy cover and greater than 50% establishment when present in the seed mix. Seed mixes of 10 or fewer species resulted in ≥ 50% of the species establishing. Idaho noxious weeds were present in less than half of the sites (47%). Cheatgrass (Bromus tectorum L. [Poaceae]), an invasive annual grass, occurred in 82% of the sites. These results provide species selection recommendations based on ecoregion for use in roadside revegetation projects in Idaho and portions of western Montana.