Although Quaking Aspen, Populus tremuloides Michaux, is not an economically important forest tree in California, it does show promise as a landscape tree, particularly because of its wide distribution and demonstrated hardiness in many climatic zones. Studies on Quaking Aspen indicate that vegetative propagation of this difficult-to-root species may be commercially feasible. Rooting of stem cuttings varies from 0 to 100% depending upon the time of year and the clone from which cuttings are taken. Cuttings treated with indolebutyric acid (IBA) have a higher rooting percentage than do the controls. Age of wood is the most important factor in rooting of Quaking Aspen. Every adventitious stem taken from root cuttings of mature trees rooted under intermittentmist conditions with IBA treatments, whereas stem cuttings from mature trees rooted only in the greenwood state. Hence, rooting of adventitious shoots may prove the best method for commercially propagating Quaking Aspen.