Perhaps no plant evokes a common vision of the semi-arid landscapes of western North America as do the sagebrushes. A collective term, sagebrush is applied to shrubby members of the mostly herbaceous genus, Artemisia L. More precisely, the moniker is usually restricted to members of subgenus Tridentatae, a collection of some 20 woody taxa endemic to North America (Beetle 1960; McArthur 1979; McArthur and Plummer 1978). As a group, the Tridentatae are distinguished from other members of the genus by a combination of traits including their woody habit, floral morphology, stem anatomy, plant chemistry, and chromosomal karyotype (McArthur 1979).