23 CFR 752.11: Federal participation.

(a) Federal-aid highway funds, but generally excluding Interstate construction funds, are available for landscape development; for the acquisition and development of safety rest areas, scenic overlooks, and scenic lands; for the development of information centers and systems; and for the removal of abandoned motor vehicles.

(b) Federal-aid highway funds may participate in any landscaping project undertaken pursuant to paragraph (a) of this section provided that at least one-quarter of one percent of funds expended for such landscaping project is used to plant native wildflower seeds or seedlings or both. The Administrator may, upon the request of a State highway agency, grant a waiver to this requirement provided the State certifies that:

(1) Native wildflowers or seedlings cannot be grown satisfactorily; or

(2) There is a scarcity of available planting areas; or

(3) The available planting areas will be used for agricultural purposes.

(c) Subject to the requirement of paragraph (b) of this section, Federal-aid highway funds may participate in plant establishment periods in or associated with landscape development.

(d) Notwithstanding the provisions of paragraph (b) of this section, Federal-aid highway funds may participate in the planting of flowering materials, including native wildflowers, donated by garden clubs and other organizations or individuals.

(e) The value of donated plant materials shall not count toward the one-quarter of one percent minimum expenditure required by paragraph (b) of this section.

(f) Federal-aid funds may not be used for assemblage, printing, or distribution of information materials; for temporary or portable information facilities; or for installation, operation, or maintenance of vending machines.