Seeds of the sister taxa Clarkia xantiana ssp. parviflora and Clarkia xantiana ssp. xantiana were subject to hydration/dehydration cycles to determine the effects of treatment on percent germination, timing of germination. Sister subspecies are indigenous to different microhabitats, with the primarily outcrossing C. x. ssp. xantiana being native to more mesic conditions while the predominantly selfing C. x. ssp. parviflora is endemic to more xeric environments. Overall, C. x. ssp. xantiana exhibited a significantly higher percent germination than C. x. ssp. parviflora. This significantly higher percent germination was more apparent for longer periods of hydration than shorter periods. There was a significant effect of seed age on germination responses to the hydration/dehydration treatment. Older seeds germinated at much lower frequency for both subspecies with significantly more families germinating in C. x. ssp. xantiana compared to C. x. ssp. parviflora. Hydration/dehydration treatment and seed age both had a significant effect on days to germination for both subspecies. The greater germination success of the outcrosser, C. x. ssp. xantiana may be attributed to its larger seeds size and/or greater genetic variability while the lower germination success of the selfing C. x. ssp. parviflora may be explained by stronger dormancy mechanisms and/or inbreeding depression.