Although prescribed fires are commonly used in management, little is known about how temperatures generated during fires affect the seed viability of species of conservation concern. We measured seed viability of six herbaceous forbs native to Ozark glade ecosystems and the glade-invading shrub Juniperus virginiana (eastern redcedar) after exposure to four temperature treatments for 15 min: 24 C, 50 C, 100 C and 150 C. Viability of Allium canadense and Ruellia humilis was reduced to near zero after exposure to temperatures of 100 or 150 C, whereas viability of Echinacea simulata and J. virginiana was only significantly reduced at 150 C. Lespedeza virginica, Oenothera macrocarpa, and Silphium terebinthinaceum maintained substantial viability after exposure to 150 C, with the proportion of viable seeds ranging from 0.3–0.5. Our results suggest that interspecific differences in tolerance to heat-related mortality of seeds may be an important factor mediating post fire patterns of plant regeneration.