At every opportunity where they are determined to be appropriate and cost-effective, the guiding principles of the E.M. should be considered to the maximum extent practicable. Successful projects take the best scientific information available and apply those solutions to mitigation problems. The E.M. and the guidelines do not require new programs to be established. They only suggest that existing project funds be used thoughtfully, with environmental protection and cost saving in mind. The intent of the guidelines is to give support to the many State highway agencies who have already taken this approach to landscape projects and encourage other States to duplicate their wisdom.
States continue to have flexibility to choose solutions appropriate to their landscape problems.
Therefore, introduced exotic species or named varieties and hybrids should not be considered native plants. Such plants would not occur naturally in an area if it were not for human activities, such as species introduction, plant breeding, and other similar cultural activities. Although the guidance encourages the collection and nursery propagation of native species, this does not mean such species become non-native once these human activities occur. Simple propagation does not alter a native species, as would intentional genetic selection for desired characteristics or other activities such as hybridizing. Commercial sources should always be your first source of plant materials.