Technical Abstract: Big sagebrush or Artemisia tridentata Nutt. ssp. vaseyana grows at slightly higher, cooler, and drier sites than does A. tridentata ssp. tridentata. The two sagebrush subspecies and natural hybrids between them are found along an elevational gradient in Salt Creek Canyon, near Nephi, UT, USA, where the parent population are separated by 85 m in elevation and 1.1 km along the transect. In 1993, three gardens were established with seedlings from five populations from different elevations planted in each garden. Physiological measurements of carbon isotope ratios, chlorophyll fluorescence, and respiratory heat and CO2 production show adaptation to the site of origin. When transplanted to foreign sites, stress was noted. Sagebrush has persistent leaves that are metabolically active all year. Seasonal changes in temperature promote metabolic responses in sagebrush that differ with population and garden.