The influence of root-zone temperature on strawberry species has not been thoroughly studied. Two experiments were conducted to determine the effect of root-zone temperature on vegetative growth, runner number, runner plant development, and water relations in Fragaria chiloensis Duch., F. virginiana Ouch., and F. viridis Ouch. In Experiment I, clones of F. chiloensis 'FRA 366' that originated in California, F. chilaensis 'FRA 606' (Alaska), F. virginiana 'FRA 67' (Maryland), and F. virginiana 'FRA 104' (Wyoming) were grown hydroponically for 21 days with root zones at 23, 29, or 35°C. All clones with roots held at 35°C had less fresh mass gain over time, fewer runners, fewer runner plants, less leaf area on mother and runner plants, and less root dry mass than plants at 23 or 29°C. Plants at 29°C had less runner plant leaf area than plants at 23°C. F virginiana exhibited greater vegetative growth and produced more runners and runner plants than F. chiloensis, but there were no species-temferature interactions. In Experiment II, F. chiloensis 'FRA 366' (mother plants originating in California and F. viridis 'FRA 333' (Germany) were grown hydroponically for 56 aays with root zones at 23, 29, 35, 20/26 (night!dax). 26/32 , or 32!38°C. F. viridis was more sensitive to high root-zone temperature than F chiloensis, and most growth reductions were associated with reduced transpiration and leaf water potential. A low temperature (23°C) promoted maximum growth of F. viridis, whereas exposure to root-zone temperatures as high as 32°C fostered maximum growtli of F. chiloensis.