This book covers all of the species that meet these two criteria (more or less):
- Regularly grow into a treelike form. It is important to understand that there is no clear distinction between trees and shrubs. To qualify as a tree a plant simply has to grow tall on a single stem, but many species can be trees or shrubs under different conditions.
- Are native or commonly cultivated north of the freeze line. All native species, and all commonly cultivated species, are included if they grow north of central Florida, southern Texas, and southern and central coastal California. In those areas there are hundreds more species of trees that are regularly cultivated, and in southern Florida about one hundred additional native species. None of these are included in the guide, meaning that the guide will not be as helpful in southern and central Florida, or in developed areas in southern Texas and California.