Plant phenology is described for plant species in galleta grass (Hilaria jamesii)-shadescale (Atriplex confertffola) and galleta grass-sagebrush (A rtemisia tridentata ssp. wyomingensis) associations in Hot Creek and Reveille Valleys of Nevada. Species within both plant associations were separated into early, late, and indiscriminate flowering groups. Duration of the species phenology cycles varied from 72 days for Indian ricegrass (ryzopsis hymenoides) to 209 days for sagebrush. The phenological cycle of individual species varied as much as 62 days in length over a 4-year period. Phenology of species common to both galleta grassshadscale and galleta grass-sagebrush associations was similar in the same year. Differences in species phenology patterns are speculated to indicate different approaches to plant survival and species proliferation, but no one phenology pattern was obviously superior. Understanding plant phenology is fundamental to understanding plant dynamics and to sound resource management of western United States shrublands. Plant phenology, the series of phases in plant development throughout the year (Lieth 1970), is an important morphological key to nutrient content (Robertson and Torrel 1958), carbohydrate reserves (Coyne and Cook 1970), and the growth rate of range species (Blaisdell 1958). Knowledge of plant phenology is useful in maximizing cattle gains and reducing detrimental grazing effects on plant species (Hormay 1970); and, in timing herbicide applications for maximum effectiveness in range restoration projects (Young and Evans 1974). In the course of the study reported here the phenology of major plant species in galleta grass (Hilaria jamesii)shadscale (Atriplex confertifolia) and galleta grasssagebrush (Artemisia tridentata ssp. wyomingensis) plant associations were recorded. The study was conducted in the Great Basin from 1969 to 1972. Species phenology among years, sites, and between plant associations were observed. Also, climate data were collected in 1972 to determine the causal mechanisms for major phenology changes (i.e., changes from vegetative to reproductive phases).