g MISC. PUBLICATION 303, U. S. DEPT. OF AGRICULTURE 



the most appropriate plant materials to be used, and such an analytical process 

 should develop selective appreciation of natural plantings upon the highways. 



The ecological or natural landscape approach to the highway planting pro- 

 gram aims to avoid the typical static, or garden-estate type of plantation design 

 in favor of fitness with the more dynamic requirements of highv/ay travel. 



Nature is to be followed as closely as possible with fullest utilization of native 

 materials or harmonizing types if the landscape development of highways is to 

 proceed * * *. It is imperative, therefore, that the landscape technician adopt 

 the broadest ecological viewpoint concerning the planting phases of the land- 

 scape development of highways. 



The use of shrubs bearing beautiful fruits automatically provides 

 food for wildlife. As Howard (%93, p. 103} has mentioned, if road- 

 side improvement designed primarily to improve the scenery is made 

 with "due regard * * * to ecological associations and as much 

 diversity as is consistent with natural groupings * * *" in the 

 plantings, it will in all probability contribute materially to the increase 

 of bird life in the immediate vicinity. 



Plantings of species effective in erosion control provide excellent 

 cover for wildlife. The danger of luring birds and mammals to high- 

 ways where wildlife mortality is undoubtedly great can be obviated 

 by placing plantings made for the production of wildlife food well 

 back from the roadway. This is ordinarily done since on highway 

 rights-of-way, plantings made too close to the road may easily become 

 a hazard for motorists. 



Highway plantings are generally given more than ordinary care. 

 Fertilizers are often used to ensure that the plants start ; and water- 

 ing, pruning, and cultivating are commonly employed to assist them 

 in growing and producing flowers or seed. Under such conditions the 

 remarks on plant competition and succession in the section treating of 

 the selection of species for planting may apply only partially or not 

 at all. 



The utilization of vegetation in highway planting is comparatively 

 new, but is rapidly increasing in importance. A recent report for one 

 State (1) mentions, for instance, that 700 miles of planting on main 

 highway rights-of-way have nearly been completed. Future work 

 may well be directed along the lines so clearly drawn by Simonson. 



PLANTS OF OBJECTIONABLE CHARACTERISTICS 



Certain species of plants possess characters that may partially or 

 entirely preclude their use in many kinds of planting. A list of these 

 would include plants that are : 



1. Poisonous to man, either when taken internally or through skin 

 irritations. 



2. Poisonous to livestock, usually internally. 



3. Secondary hosts to economically injurious fungi or insects. 



4. Susceptible to the ravages of insects the control of which is 

 difficult. 



5. So exceedingly vigorous and aggressive as to crowd out more 

 valuable or useful species. 



It is rare to find a situation in which plants possessing one or several 

 of the above characteristics cannot be used. However, it may often 

 be advantageous to substitute forms less objectionable, a procedure 

 which is usually easy since the site is very unusual upon which at 

 least two species of good character cannot be grown. 



