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Roadside Use of Native Plants

Designing Roadsides With Native Plant Communities— How to Work with a Disturbed Site and Reflect Local Character

Darrel G. Morrison, School of Environmental Design, University of Georgia

The roadside environment is one of the most- frequently experienced landscapes in this country. The view from the road is often the only exposure to the local landscape experienced by travelers. The right- of- way, then, provides an opportunity to heighten the public's understanding and appreciation of the unique local or regional landscape. While our sense of place is influenced by many factors (e.g., the presence or absence of rock outcroppings, the color of the soil), the native plant communities of a region provide some of the strongest cues to the unique identity of a place. It follows, then, that a worthwhile objective in the design and management of roadsides would be to incorporate within the roadside landscape groupings of plants which are representative of native plant communities.

There are, of course, many constraints in taking this approach to roadside landscapes. To begin with, the environmental conditions within the roadway corridor may be quite different after construction then they were earlier. For example, where there may have been a uniform slope across the right- of- way before construction, there may now be a complex of slopes and swales with a variety of soil types, moisture conditions, and solar aspects after construction. Furthermore, visibility and safety concerns may dictate that certain zones not be designated for native forest community plantings, but forest edge, savanna, or a native grassland community.

In planning a roadside landscape based on native plant communities of a region, a first step is to analyze and characterize the different zones in terms of environmental conditions; e.g., soil type, moisture characteristics, solar orientation, existing vegetation, and adjacent land use/cover. These zones should be plotted, and then another drawing showing zones with limitations on vegetation size or growth form can be overlain. Using these as a guide, a mass/space diagram can be created, in which the "mass" areas may be designated as target forest/forest edge plant communities, and "spaces" may be designated as relatively low growing plant communities such as prairie, sedge meadow, or other predominantly- herbaceous groupings. Specific plant species to be incorporated into the different designated communities may be determined from a survey of ecological literature for the region, and from field observation of the plant community types designated for the right- of- way. It is difficult, if not impossible, to recreate a native community in its entirety, but we often can incorporate key species of a plant community within appropriate zones. These include the dominant species (usually the largest members of the community, influencing everything beneath them) the prevalent species (those which typically occur most abundantly in the community), and the "visual essence" species (those which have some unique trait which give them visual importance in the community).

Because of the nature of roadsides as disturbed environments, it may not be possible to introduce all the desired species of a particular forest community at the initiation of a community- based roadside design, but the initial planting and subsequent management can facilitate their establishment over time, either by natural invasion or by later introduction when conditions are right for their establishment. Grassland/meadow communities in most cases will need to be mowed annually and/or periodically burned, to suppress unwanted woody invaders. And as in any native community planting, vigilant monitoring of invasive exotic species is a necessity, along with strategies for their suppression or removal.

Using a native community approach in the design of roadsides is not a laissez- faire approach, but the potential rewards in terms of perpetuating and restoring native plant communities and a real "sense of place" to the highway environment, are great.

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Questions and feedback should be directed to Deirdre Remley (deirdre.remley@dot.gov, 202-366-0524).

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