Author Bassuk, N., Curtis, D.F., Marranca, B.Z. & Barb, N.

If there is no one perfect tree, it is because there is no one homogeneous urban environment or site. The urban environment is a conglomeration of soils, microclimates and other site conditions. Both above ground and below ground conditions can change dramatically in the space of ten feet. Needless to say, the lists of trees that follow are provided only as a guide for selection. A comprehensive site assessment should occur which considers plant requirements such as climate and microclimate considerations (hardiness zone, light conditions, heat, wind), soil factors (pH, texture, compaction levels, drainage characteristics, yearly salt application), above-ground limitations (wires, proximity to structures), and below-ground limitations (rooting space, utility issues). Only when there is a thorough understanding of the environmental variables at a potential planting site will we be able to make appropriate tree selections. The cost of skipping this step can be counted by dead or poorly growing trees and unrealized benefits to the community. A reasonable strategy for most urban plantings is to limit any one species to between 5% and 10% of a total urban population. Consequently, if a disease or insect infestation should occur, 90-95% of the tree population would remain unaffected and intact. Unfortunately, in most urban areas perhaps only five or fewer species make up the great majority of trees planted.