23 CFR 752.4 - Landscape development.
(a) Landscape development, which includes landscaping projects and other highway planting programs within the right-of-way of all federally funded highways or on adjoining scenic lands, shall be in general comformity with accepted concepts and principles of highway landscaping and environmental design.
(b) Landscape development should have provisions for plant establishment periods of a duration sufficient for expected survival in the highway environment. Normal 1-year plant establishment periods may be extended to 3-year periods where survival is considered essential to their function, such as junkyard screening or urban landscaping projects.
(c) In urban areas new and major reconstructed highways and completed Interstate and expressway sections are to be landscaped as appropriate for the adjacent existing or planned environment.
(d) In rural areas new and major reconstructed highways should be landscaped as appropriate for the adjacent environment. Planning should include the opportunity for natural regeneration of native growth and the management of that growth.
(e) Landscaping projects shall include the planting of native wildflower seeds or seedlings or both, unless a waiver is granted as provided in § 752.11(b).