Dirr has put together a first-class A to Z guide of the best woody plants for cooler climates, particularly for gardeners in hardiness zones 3 to 7. The book contains copious information on the flowers, fruit, bark, fall color, habit, etc., of more than 500 species and 700 cultivars. A straight shooter, Dirr is generous with his praise for deserving trees and shrubs such as the sugar maple, “The true nobility of fall-coloring trees - challenged by many, rivalled by none,” but he can also be frank with his scorn for those that don't live up to expectations, “In all my traveling and consulting work, I have never recommended, at least when conscious, a poplar.”
Dirr's Hardy Trees and Shrubs has excellent photographs showing the size and shape of the mature tree or shrub, as well as close-ups of the leaf, bark, and fruit. Each plant has the botanical name, common name, description and many candid comments, such as for the Italian Alder, “Deserves a longer look by American gardeners.”
Numerous lists in the back of the book cross-reference trees and shrubs by both their botanical and common name for easy perusal to find the right plants for a variety of conditions or with a particular characteristic.