Penstemon (pronounced /ˈpɛnstɨmən/), 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. Classical taxonomy maintains the traditional placement in Scrophulariaceae.
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.
Native Americans long used penstemon roots to relieve toothache. John Mitchell published the first scientific description in 1748; although he only named it as Penstemon, we can identify it as P. laevigatus. Linnaeus then included it in his 1753 publication, as Chelone pentstemon, altering the spelling to better correspond to the notion that the name referred to the unusual fifth stamen (Greek "penta-", five). Mitchell's work was reprinted in 1769, continuing with his original spelling, and this was ultimately accepted as the official form, although Pentstemon continued in use into the 20th century.
Although several more species were found in the 18th century, they continued to be classified in Chelone until about the 1820s. The period of 1810 to 1850 increased the number of known species from 4 to 63, as expeditions travelled through Mexico and the western United States, followed by another 100 up to 1900.
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