Gucker, Corey L.; Shaw, Nancy L. 2022. Thickleaf beardtongue (Penstemon pachyphyllus). In: Gucker, C.L.; Shaw, N.L., eds. Western forbs: Biology, ecology, and use in restoration. Reno, NV: Great Basin Fire Science Exchange. https://westernforbs.org/species/thickleaf-beardtongue-penstemon-pachyphyllus/