Penstemon species are commonly called beardtongue because of an interesting adaptation to attract pollinators. "One of the five stamens is sterile and does not produce pollen. It is often modified into a hairy or bearded tongue and probably attracts insects," as noted in the field guide Wildflowers of Iowa Woodlands by Sylvan Runkel and Alvin Bull.
Penstemon grandiflorus is common on Loess Hills prairies in western Iowa but very infrequent elsewhere on dry, sandy prairies and stabilized sand dunes. Its purple flowers bloom from late May to mid-June.