Alfred Rehder was the curator of the Herbarium of the Arnold Arboretum. He was German-born and a self-taught taxonomist, arriving at the Arboretum in 1898 and first employed to weed the shrub collection. His keen taxonomic judgment was quickly recognized, however. The Manual of Cultivated Trees and Shrubs Hardy in North America Exclusive of the Subtropical and Warmer Temperate Regions, best known as "Rehder's Manual," was first published in 1927. Here we have reprinted the second edition, published in 1940. Alfred Rehder's book was designed to complement Sargent's Manual of the Trees of North America (Exclusive of Mexico)and Gray's Manual of Botany, which documents the native vegetation of the same region. Rehder's goal of a concise compilation of all the woody plants known to be cultivated in eastern North America was achieved in the volume. For each of the 2,300 species of trees and shrubs covered in the book, Rehder included a concise physical description, as well as time of flowering and fruiting, references to published illustrations, region of native habitat, date of introduction into cultivation, hardiness zone, and comments on horticultural merit or special cultural requirements. He gave distinguishing features and pertinent information for 2,465 varieties. Brief mention was included of another 1,265 species and 507 hybrids that were either less well known or rarely cultivated. Its value to gardeners, arborists, botanical garden curators, and anyone else needing to identify trees and shrubs became readily apparent.