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Roadside Use of Native Plants

Roadside Use Of Native Plants — Introduction

"The earth's vegetation is part of a web of life in which there are intimate and essential relationships between plants and the earth, between plants and other plants, between plants and animals. Sometimes we have no choice but to disturb these relationships, but we should do so thoughtfully, with full awareness that what we do may have consequences remote in time and place."
– Rachel Carson, Silent Spring, 1962

And the decisions we make, can no longer be the same ones we have always made, especially on the sides of the road that cover and cross millions of acres. One size does not fit all. One standard seed mix will not succeed in every site. One book of standard specifications for seed mixes no longer matches the reality of the objectives of any given planting, in any given state.

Since highway construction began, the engineering objective was to establish a green growing slope stabilizer. Because of NEPA and the Clean Water Act, the environmental objective changed to a quick green growing slope stabilizer. Because of beautification concerns, the esthetic objective was to establish a visually- pleasing, quick, green- growing slope stabilizer. Because of vegetation management issues, the maintenance objective is becoming, establish a noninvasive, visually- pleasing, quick, green- growing slope stabilizer. Because of diminishing resources, a holistic objective must be to establish an affordable, noninvasive, visually- pleasing, quick, green- growing slope stabilizer. This growing list of roadside objectives makes the seed mix solution complex, and one standard specification cannot meet all the objectives.

Just as one size does not fit all, one seed mix will not succeed in every part of a State or every part of the country. Texas has defined 26 natural regions in that State alone. One seed mix to suit all construction sites across any State was always simplistic, albeit convenient. Soils, moisture regimes, topography, adjacent vegetation, existing seed bank, are always variables — no combination of which is the same from site to site. Therefore the notion of one seed mix could never be reliable, unless introduced plant species with wide ranges of tolerance were used. This has been the case across the country. Species like reed canary grass, sweet clover, perennial rye, smooth brome, and crownvetch have consequently become weed problems themselves, in some instances because plants with wide tolerances of soils, climates, etc. tend to be competitive and capable of not only surviving, but moving beyond where we plant them. They are no longer the best practice under any conditions. They are beginning to show up outside the right- of- way fence. They are beginning to show up on State noxious weed lists! They are costing us too much environmentally. They are costing us too much in the realm of public opinion, as well.

Therefore we must take the time to be site specific with our analysis and our designed solution in each roadside project. The investment in time will pay off in the long run, both economically and environmentally. Our roadside decisions will be noticed. Look out the nearest window — and consider the face of the land. What you see is a human creation. The tree or shrub or patch of grass is there, in other words, either because men put it there or because they allowed it to remain. Roderick Nash, The American Environment, 1976.

The contents of this book are aimed at making those site specific decisions. The primer gives a holistic background for those decisions. It also addresses some basic techniques and misconceptions about using native plants. The State by State section pulls together native, endangered, and noxious plant lists to aid design and management choices. Resources for more information are included. The appendix adds definitions, bibliography, and policy citations to clarify any debates about the purpose and direction of the use of native plants on roadsides.

This ecological approach involves a lot of common sense. This book attempts to provide technical information to supplement that common sense for more successful projects. The Federal Highway Administration has made a commitment to using this approach and hopes that you find this handbook useful.

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

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