Penstemon (tribe Cheloneae: Plantaginaceae) is a large genus (about 282 species) of perennial plants endemic to North America, ranging from Alaska to Guatemala and from coast-to-coast, exclusive of the Canadian shield. It has been divided into six subgenera : subg. Penstemon (eight sections, 22 subsections, ca. 199 spp.), subg. Habroanthus (two sections, 46 spp.), subg. Saccanthera (2 sections, 3 subsections, 26 spp.), subg. Dasanthera (nine spp.), subg. Cryptostemon (monotypic), and subg. Dissecti (monotypic) (taxonomy based on Bennett et al. 1987).
Floral colors include white, yellow (rare), blue, violet, purple, pink, magenta, and red. Corollas can be tubular, funnel shaped, bell shaped, or widely expanded. The flowers are pollinated by bees, wasps, moths, butterflies, flies, and hummingbirds.
Penstemons, also known as beardtongues, are becoming ever more important in the landscape. All species of Penstemon are native to North America. Every state in the continental U.S. includes at least one species of Penstemon. The greatest number of species are found in the intermountain region of the Southwest (Utah has 73 species!). The number of species decreases rapidly east of the Rocky Mountains, with only about 24 species found east of the Mississippi River.
"Penstemons, sometimes called beardtongues, are a fascinating group of plants, little known to the average gardener. To wildflower lovers and gardeners alike, penstemons offer beauty unexcelled by any other wildflower." - American Penstemon Society
Penstemons are found in many interesting habitats, and many species are adapted to specific substrates such as limestone, deep sand, oil shale, and volcanic soils. The flowers range in colors across almost the entire spectrum, with vivid reds, magenta and violet, intense shades of blue and purple, pink and lavender, often beautifully blended to white and cream. Some of the most striking flowers are intensely colored on the outside and bright white inside the corolla tube. Yellow is an unusual color in penstemons, but it does occur rarely - mostly as pale yellow to creams.
Most species bloom during March and April in the southwest United States, May and June in the mid-latitudes, June in the northern states, July in Canada, and August and September in Mexico. Many penstemons are also interesting plants for flower arrangements. Cut inflorescence stems last a week or more in a bouquet.
Members of the American Penstemon Society grow a variety of species in the landscpape, from the most common to a few of the rarest. There are still many species that have not been introduced into cultivation. However, cultivars are often found in garden centers, and most species of Penstemon are suitable for xeriscaping. Penstemons require minimal care in the landscape - they are adapted for drier conditions in the wild, which makes them ideal for the casual gardener.