Roadside Use of Native Plants

Utilizing The Ecotype Concept — An Insight into Native Plant Establishment

Wayne G. McCully, Texas Transportation Institute, Texas A&M University

An Executive Memorandum issued by the President in 1994 calls for planting native grasses and forbs (broad-leaf herbaceous plants) on federally-funded projects. State highway agencies (SHAs) have reported a wide range of success in establishing native plants and feel their use is practicable. Failure to secure a stand may be due to a number of causes such as seeding plants which are not adapted (at home) or planting at the wrong season. More likely, lack of performance may signify that the seeded materials were placed in an unfavorable environment.

All cultivated plant varieties began as wild plants. Range scientists and agronomists have shown that individual species having a large geographic distribution vary considerably in plant height, growth habits, earliness of maturity, leaf characters, reproductive habits, and other characters. These characters are not distributed at random throughout the range of the species. Instead, plants showing these variations are grouped into local ecological units associated with habitat differences. These local ecological plant groups are known as ecotypes or biotypes. Ecotypes are plants in the early stages of varietal development, but lack the refinement in plant characters which come with breeding to fix the desired characters.

Ecotypes were first recognized in the early 1920's by scientists studying taxonomy, morphology, ecology, and physiology. Ecotypes assembled in a common garden demonstrated that:

• Northern ecotypes of sideoats grama flower earlier than more southern ecotypes, resulting in shorter plants.
• Ecotypes of little bluestem growing on either sandy or clay soils do not grow well on soils of the opposite texture.
• Within a single species tall plants grow in lowlands and dwarf plants grow on uplands. Plants with coarse leaves are found in hot, sunny situations while those with broad, thin leaves grow in shade.

In a practical sense, ecotypes are considered best adapted to conditions within 100–200 miles from the center of origin or point of collection. The usual considerations include soil type, day length, elevation, exposure, and climatic factors. All of these factors seem to be associated with a common genetic base. State experiment stations, U.S. Soil Conservation Science and the National Park Service have been involved in plant selection for isolating ecotypes or utilizing ecotypes for operational plantings. A complete program will involve research at the state level, by federal agencies, and endorsed by the seed industry.