ABSTRACT We investigated the seed production and germination requirements of Penstemon oklahomensis, a species of conservation concern, to determine interannual variation in seed production and germination requirements. Mature seed capsules were collected and seed numbers counted in two successive years to assess interannual variation in seed production. A significant difference in number of seeds produced was found between collection years. Germination trials were conducted using the seed collected and subjected to three stratification treatments in two soil types. Seeds held over from the first collection year were also germinated to investigate viability loss a year after collection. Survival analysis was used to estimate the probability of seed germination under the treatment conditions. Germination probability was highest for seeds that underwent a cold stratification period of 60 days if sown the same year as they were collected, regardless of soil type used. Seeds held over a year had higher germination probability after a 30-day cold stratification period, but the probability was lower than the same treatment when the seeds were sown during the year collected. Seed production and germination requirements for P. oklahomensis are similar to other species of Penstemon, both in the Intermountain West and east of the Mississippi River.