Beardtongue — Penstemon (Beard-tongue) is a large genus of North American and East Asian plants traditionally placed in the Scrophulariaceae family. Due to new genetic research it has now been placed in the vastly expanded family Plantaginaceae.
They have opposite leaves, partly tube-shaped and two-lipped flowers and seed capsules. The most distinctive feature of the genus is the prominent staminode, an infertile stamen. The staminode takes a variety of forms in the different species; while typically a long straight filament extending to the mouth of the corolla, some are longer and extremely hairy, giving the general appearance of an open mouth with a fuzzy tongue protruding and inspiring the common name beardtongue.
Most penstemons are herbaceous perennials, the remainder being shrubs or subshrubs. Heights can range from 10 cm to as much as 3 meters.
The one Asiatic species previously treated in Penstemon is now placed in a separate genus Pennellianthus. This leaves Penstemon a mostly nearctic genus, with a few neotropical species. Although widespread across North America, and found in habitats ranging from open desert to moist forests, and up to the alpine zone, they are not typically common within their range.
Despite being among the most attractive native flowers of North America, Europe has always been far more active in the development of penstemon cultivation, and hundreds of hybrids have been developed since the early 1800s. The earliest development is somewhat shrouded in mystery; for instance Flanagan & Nutting’s 1835 catalog mentions a ‘Penstemon Hybridum’ but does not describe it.