Postfire restoration of sagebrush steppe is limited by poor sagebrush establishment from seed. Transplanting may improve seedling establishment, but it requires more labor and expense. Given variable transplant survival in big sagebrush (Artemisia tridentata Nutt.), establishing links between restoration practices and survival related to exposure to adverse weather, via plant response to stress, could significantly improve transplant efficacy. We tested how planting season and transplant age (size), two restoration practices likely to affect seedling survival across a range of environmental conditions, related to transplant survival and stomatal conductance, an indicator of seedling ecophysiological performance. We found low mean stomatal conductance during key periods in spring and early summer was associated with subsequent growing season mortality across all size-classes. Overall, these findings suggest managers should consider the importance of plant performance during key stressful periods in evaluating transplant survival related to restoration methods.