Penstemons, America’s Premier Wildflower
Continuing the Spring Bloom with Native Wildflowers
One of the biggest genera to star in mid to late spring and into summer are the penstemons. They are the Southwest’s star wildflower. Penstemons are endemic to North America and can be found in every biome across this huge continent from Alaska to Guatemala, but most are native to arid and semi-arid areas in Western states, with the center of species diversity in the Four Corners region of Utah (71 species), Colorado (62), Arizona (43) and New Mexico (42). Forty six species live in Idaho, 45 species in Nevada and 39 in Wyoming. About two dozen penstemons are native to Texas. (Numbers of species per state will vary by source.)
With between 250-280 species, and many, many hybrids, there are multiple species of penstemon to suit your garden conditions. Natively, penstemons grow on sandy desert floors, in mountainside scree, among pinyon/juniper woodlands, oak scrub, ponderosa and aspen forests, and upwards to sub-alpine and alpine terrains. Penstemons thrive in prairie grasslands and deciduous woodlands of the eastern half of the United States. Penstemons find home in sand dunes to generally sandy soil, among rocky scree and talus, in clay soil, and in calcareous limestone soils in the plains and the West. They readily colonize on disturbed land, commonly along road cuts and along highways and are included in wildflower mixes. Just about anywhere one hikes in the West in America's national parks and monuments, spring into fall, you are likely to see at least one species of penstemon. To me, seeing these wonderful garden flowers in their natural setting is a thrill. They are usually spotted growing singly, here and there. Occassionally, one will find drifts of penstemons happily thriving.
Western penstemons have adapted to life in soils with scant organic content, as have most other drought tolerant plants. Penstemons in areas prone to wildfires have adapted to this condition as well. Studies have shown that smoke from wildfires increase the germination rates of many penstemon species, in addition to many other plant species in ecosystems around the world. (Smoke, Seed Germination and Penstemons.)
East of the Mississippi, the penstemons can be found growing among sandy and better loamy soils. Nearly all penstemons prefer alkaline soil. Penstemaniacs across the world treat acid soils with limestone to be able to grow penstemons, even into Scandinavia.
Although the majority of Penstemon species are native to the west, the species was first described by John Mitchell in 1748. It is thought to be the eastern smooth beardtongue, Penstemon laevigatus, (then Chelone pentstemon) native from Pennsylvania, New Jersey south to south central Alabama to Florida and along the eastern seaboard.
Penstemon comes from two Greek words, pente meaning five, and stemon the name of the male flower part we call a stamen. The genus name means having five stamens, four fertile and the fifth is called a staminode and is sterile. This sterile stamen structure sometimes has a hairy tip and is located at the throat of the floral tube, hence the other common name for flowers in this genus, beardtongue. (Photo at left showing the beard and open bulging corolla, P. palmerii.) John Mitchell originally spelled the name Penstemon, instead of Pentstemon, as one might think. Linnaeus attempted to correct the spelling, but the original (mis)spelling survives as the official genus name, however references may sometimes (incorrectly) show the genus name as Pentstemon. Penstemon has recently been moved into the Plantaginaceae (plantain) family from the Scrophulariaceae (figwort) family due to DNA testing.
Penstemons exhibit a variety of stem, leaf and flower shapes and arrangements. A few species can be as tall as 5 ft. (Penstemon alamosensis), others are no more than three to six inches displaying a mat form (P. pinifolius and P. caespitosus). Leaves can be thick or thin, narrow or wider, green to blue to gray in color. Most penstemons form a dense rosette of leaves, blending into the landscape when not in flower. Flower shapes are tubular corolla (photo at upper right, P. cardinalis); funnel-shaped, a tulublar flower that inflates, similar to a funnel (photo right, P. clutei); or a bulging or open corolla (Photo at left, P. palmeri). Many of the hybrid penstemons have open, bulging corollas. Penstemon species are in nearly every color, but the majority are whites, pinks, lilac, rose, purples, reds, red-orange and just a few yellows and bloom from the bottom of the stem to the top. Many species have darklines on the lower inside part of the corolla called guidelines, that act as nectar guides for pollinators. These guidelines are much more visible to us in the bulging flower shapes (Penstemon palmerii at upper left).
Many penstemons with white, blue and purple flowers have bulging corollas are pollinated principally by bees and wasps (Penstemon fendleri), with many of the red, orange-red and pink flowering species with tubular corollas (Penstemon eatonii) are pollinated by hummingbirds (Insects that Visit Penstemon Flowers). Penstemons with funnel shaped flowers come any color. Roughly 80% of penstemons are pollinated by bees. Moths and long-tongued bees can also pollinate flowers of the genus whose flowers are partly bulging and part tubular (funnel-shaped), such as Penstemon clutei. Moths also frequently pollinate white flowered species; flies and butterflies provide limited pollination service. Bumblebees are very active visitors to penstemons flowers with the wider, bulging corollas. Many insects depend on penstemon for nectar and pollen as nourishment, regardless of their pollination service. (Photo of P. parryi at left, with hummingbird!)
Penstemons and Gardening
Penstemon is one genus that sings “right plant, right location” louder than most. All prefer full sun, even the full, intense southwestern sun. Penstemons native to woodlands, whether western or eastern woodland, can take part shade. Western xeric penstemons need drier garden conditions, and those native to the Great Plains, northward and eastward can be located in mesic or more irrigated areas of the garden. Many of the penstemons can be short lived, even under their ideal condition. (Photo at left is P. pachyphyllus at Hovenweep National Monument, Utah.)
Penstemons were sparsely featured in American gardens until the advent of the native plant movement and xeriscape gardening. However, British and other European plant breeders began experimenting with several species to adapt penstemons to their gardens around 1900. An article about penstemons in The Guardian noted that a nursery in Scotland boasted having 500 hybrids of penstemon in 1900. Principally, these hybrids came from penstemons that are native to higher elevations and moister areas and crossed with Penstemon cobaea, the foxglove penstemon ; P. triflorus, native to the Texas Hill country, the three-flowered penstemon similar to P. cobaea; and P. hartwegii, a bright rose-red, large flowered penstemon native to higher elevations near Mexico City. These three species produced hybrids sometimes referred to as the “Henry Hybrids” -- a wide range of bedding penstemons grown in the UK and Europe. Since then, many other species have been used in hybridization, mainly the penstemons with the open, bulging corollas. These large, colorful European hybrids struggle to overwinter back in their native North America, except in milder climates, being cold hardy to 10° or 15°, (they are borderline hardy for the Texas Panhandle). Over the years, nearly three dozen penstemon hybrids have gained the Royal Horticultural Society Award of Garden Merit.
Americans finally banded together to give penstemons their due. In 1946, the American Penstemon Society (APS) was formed for the identification, study, enjoyment, promotion and protection of penstemons throughout the United States. Their website includes much useful information about penstemons, especially information on known species, as well as a list for seed sources. Members participate in seed exchanges. If you are interested in trying penstemon species whose seed is not commercially available, one might consider joining. The APS publishes a newsletter with scolarly articles on penstemons and information on penstemon nature hikes. (P. barbartus 'Rondo Mix Purple' at right.)
The North American Rock Garden Society relies on the lower growing and mat forming penstemons to bejewel their gardens. I admit to having no experience with these, but many rock gardeners do. The Society has an extensive list of penstemons in their seed exchange, and a web page with good photos, worth checking out. Rock gardening with penstemons and other low growing plants is an ideal gardening style for the Texas Panhandle's windy climate.
I first heard about penstemons when the Penstemon digitalis cultivar ‘Husker Red’ was named the “Perennial Plant of the Year” by the Perennial Plant Association in 1996. This was about the same time as perennial plants were really making a move into our gardens. ‘Husker Red’ was selected by Dale Lindgren of the University of Nebraska. I’ve tried it since, but haven’t found it long-lived or as stunning as it is in rainier, more humid climates. The Brits positively adore it. (Hybrid at left, P. x mexicali cultivar.)
Both the Plant Select Program and GreatPlants for the Great Plains have recognized several penstemons as exceptional plants for their region. Penstemon barbartus 'Twizzle Purple' is 2017 All American Selection. High Country Gardens offers many penstemons suitable for high plains gardens, including a few hybrids. They’ve been a leader in native plant hunting, breeding, and supply for several decades. Today, many, many penstemon hybrids are being developed in the United States. A number of California growers and nurseries offer what is termed “border” penstemons for use as bedding plants. These are said to be cold hardy down to 15°, possibly 0°. Digging Dog Nursery and Joy Creek Nursery have many cultivars and hybrid penstemons for sale. Star Roses and Plants recently introduced what they call the Rock Candy Series of penstemons and are hardy in Zones 5-9. Swallowtail Garden Seeds is one source for hybridized penstemon seeds. Western Native Seed and Plants of the Southwest are two additional penstemon seed suppliers.
Penstemons are easily grown from seed. Locally, Neal Hinders, owner of Canyon’s Edge Plants in Canyon, TX, grows a wide number of penstemon species, many of them mentioned in the dry, xeric section below. It is from Neal that I first started to try different xeric species, after my initial trial of ‘Husker Red’ ended.
In the Southwest, penstemons go hand in hand with growing plants for hummingbirds and bee pollinators. “Penstemons, to me, are the ultimate hummingbird plant in the spring,” said Hinders last week when I went penstemon shopping at his nursery. “With different varieties planted out, you can have early spring blooms and then other species bloom for the late spring migrating hummingbirds. Penstemon wrightii is a species that is very showy and long blooming plant, as showy as our Texas Red Yucca,” he continued. Hinders has many different species in his display garden, and several, including Penstemon ambigua, P. wrightii and P. cardinalis were in still in bloom at mid-August. (Photo of P. wrightii at right.)
Penstemons for Dry, Xeric Beds and Borders
Penstemons native to arid and semi arid areas in the western states are extremely well suited to xeric beds and borders in the Texas Panhandle. They prefer soil that has good drainage, so it seems strange that many species will grow well in clay soil amended for drainage, but using only minimal amounts of organic matter. Sand, Turface and expanded shale are three inorganic amendments to use. For some tips on amending beds, click here.
Some species penstemons generally have short 2-4 week bloom periods, some can go 6 – 8 weeks or bloom over the entire season when provided what gardeners consider inhabitable conditions. Because of gardener's inclination to, say, garden, penstemons are often short-lived. But when tried, these xeric penstemons liberally planted among agave, cactus and yucca will cause penstemonium to break out in the bed. (photo at right, P. eatonii in High Desert Garden at Amarillo Botanical Gardens.)
I have only grown about a half dozen species of penstemon, Penstemon eatonii has been the longest lived by far, about 5-7 years. Since this study, I’ve planted more, but am severely limited in trying more due to space. Penstemons don’t like to be crowded – give them room. What I think the many references I’ve read means by this, is that penstemons require full sun, and in arid places, spaced further apart so as to get enough available moisture. The Texas Panhandle naturally receives adequate rainfall (excepting drought years) so as to eliminate the need for irrigation. Having said that, there are exceptions. Robert Nold, author of Penstemons, recommends irrigating new plants adequately in the spring to establish them and aid in blooming. If planting penstemons in a xeristrip, that narrow strip of land between the sidewalk and street, don’t shovel winter’s snow on them. (P. clutei and Santa Rita prockly pear cactus at right.)
Penstemons can be planted in the spring or the fall. Hinders encourages fall planting: “They establish during the cooler months and are ready to take off for next season’s blooms.” Canyon’s Edge Plants still has a good selection still available this fall.
In xeriscape beds and borders, the penstemons suited sing a song of low maintenance, liking their home dry, well drained, sunny and undisturbed. Even if for no explicable reason they disappear after a year or two, they are worth restocking. To perpetuate penstemons in the bed, let them go to seed, scattering seed after deadheading.
Nearly any plant suitable for xeric bed or border is good accompaniment for pentemons. Flowering penstemons enliven agave, yucca, and cactus at the same time creating a sense of place in your garden. California poppies, blue flax, and bluebells add spring sparkle, along with native calylophus, evening primrose, Blackfoot daisy, chocolate flower and numerous salvias.
Here are a few of the 250-280 species to try. The American Penstemon Society has profiles and information on most of them.
The firecracker penstemon, P. eatonii, grows up to 40 inches, the top part of the stem is red, with green glossy leaves. Its scarlet red tubular flowers put on a spectacular show in May. Firecracker penstemon has a wide native distribution from western Texas and west to Nevada and California. (Photo left.)
Sunset crater penstemon, P. clutei, grows up to 40 inches, but usually shorter. Sunset crater penstemon’s glaucous leaves are a blue-gray and the flowers a bright pink with prominent guidelines. It’s a charming, appealing penstemon in any xeric garden. It has a narrow native range limited to Sunset Crater near Flagstaff, AZ, but a very large adaptable range, and is rated cold hardy down to -20°. (Photo shows a hawkmoth, below right.)
The most fragrant of the penstemons is Palmer’s penstemon, P. palmeri, native to California, Arizona, Utah, SW Colorado, Nevada and southern Idaho in elevations 4000 – 6000 feet and can reach up to 4 feet tall.. Palmer's penstemon displays one of the largest flowers, if not the largest. It’s large, pale, almost whitish pink to darker pink flowers display darker guidelines. It blooms May to August in the Texas Panhandle (overall in native range it can bloom from March to September). This plant thrives in the dry garden when kept dry or it will act as a delightful annual/biennial. (Photo at right.)
The scarlet bugler, Penstemon barbatus, is native to Western Texas and westward to Arizona, south to Mexico, but not known to be native to the Texas Panhandle. However, it grows here nicely, reaching a height of 24-30 inches with red tubular flowers in May and early June. P. barbatus is one of the parents of some hybrids and cultivars that are suited to organically amended soil and more frequent irrigation, such as P. barbartus ‘Elfin Pink’ and ‘Schooley’s Yellow’.
A mid to late summer blooming penstemon is the cardinal penstemon, P. cardinalis, with two subspecies, cardinalis and regalis. Cardinal penstemon is a hummingbird favorite with dull red downward-facing tubular flowers and gray-green leaves up to 2” wide. It is native to the White Mountains of New Mexico. Blooms July to September. (Photo at left.)
Scarlet bugler penstemon, P. centranthifolius, is another hummingbird favorite. Bright red tubular flowers on large showy multi-stemmed plants up to 4 feet tall. The red flowers appear yellow in the bud. It’s native to the foothills of southern California.
Another penstemon that performs quite well in the Texas Panhandle, according to Hinders of Canyon’s Edge Plants, is Alamo Canyon Penstemon, Penstemon alamosensis, native to southern New Mexico. It bright coral-red flower is an expanding tube with a symmetrical face. Blooms May to early June.
Similar in appearance to P. clutei is Parry’s penstemon, P. parryi, a Sonoran desert native. It is much more cold hardy than its native range indicates, growing well in the Texas Panhandle. Parry’s penstemon grows to 3-4 feet tall with narrow bluish leaves that clasp the stem. Rosy pink flowers form a narrow tube that expand at the end in a wide mouth, funnel-shaped. The blue-leaved plant offset by deep pink bangles sparkle among the cactus and agave when we visit desert gardens in mid-March. Here, they bloom later in spring. Parry’s penstemon is named afer Charles C. Perry, the great botanist.
Superb penstemon, P. superbus, is another stunning species for the Texas Panhandle. A tall growing species, it will reach five feet with scarlet tubular flower and wide leaves. Superb penstemon can be found growing at elevations of the pinyon-juniper communities at 3500-5500 feet, in sandy, gravely and rocky canyons and washes of Arizona, New Mexico, and northern Mexico.
Desert beardtongue, another penstemon native to hot, dry environments is P. pseudospectabilis, a real mouthful. Desert beardtongue can be found growing near Las Vegas, Nevada, east and south, and up to elevations of 7000 feet, making it completely cold hardy for the Texas Panhandle. I have found this penstemon to be short lived, usually no more than 3 years. But it is a stunner, growing usually to 3 feet, with green, toothed, clasping leaves -- leaves appearing disk-like around the upper stem. The flowers are deep rose, tubular with a widening throat. Blooms May to July. Most likely, desert beardtongue needs pretty good draining soil. In the winter, the green leaves turn a deep blue-green, with the underside purple. An attractive plant I was always sad to lose. (Photo at left.)
One of the last penstemons to bloom is Bridge’s Beardtongue, P. rostriflorus (formerly known as P. bridgesii), blooming from July until frost. Bridges penstemon grows to 2-3 feet tall with long narrow gray-green leaves and orange-red tubular flowers hang downward from thin stems. Bridges penstemon is a very long lived species. It is native in sunny mountainous areas of California east to Colorado and New Mexico.
Our local and surrounding plains native penstemons are Penstemon albidus, ambiguus, buckleyi, fendleri, and wrightii.
White flowered penstemon, Penstemon albidus, has the widest distribution of any species in the Great Plains from Texas north to Alberta, west to New Mexico and east to Manitoba. It grows 4-16 inches tall and is usually found in open grassland. Moths pollinate the white, fragrant flowers, sometimes streaked with lavender. (Photo at right.)
Plains pink, sand or bush penstemon, P. ambiguus, grows to form what resembles a small bush, 6- 20” with a woody base. It’s native range extends from northeastern Colorado down to Chihuahua, Mexico. Masses of pinkish-white pansy-faced flowers are arranged in a raceme-like inflorescence atop upright wispy stems and subject to flopping over in full bloom in moist conditions. Leaves are thin, light green filiform. Plains pink penstemon will be a long lived plant if not watered much. (Photo at left.)
Buckley’s penstemon, Penstemon buckeyi, grows from 12 – 16” tall in dry sandy plains and grasslands of Southeastern New Mexico and Colorado, east to central Kansas and West Texas including the Texas Panhandle. It’s pale blue to lavender flowers, with purple guidelines, are lightly bearded and are borne on a dense, leafy spike-like cluster, interrupted along the height of the spike.
Wright’s penstemon, P. wrightii, sometimes called Texas Rose penstemon, is native north of Big Bend National Park and into the Davis Mountains of Texas. Bright red to pink tube-like flowers end with an inflated corolla. Broad 3” gray-green leaves that are clasping around the stems can grow to 2-3 feet tall. Blooms in June, July and into August in the Texas Panhandle.
One might run across several of these native penstemons while hiking in Palo Duro Canyon and Wildcat Bluff, especially Fendler’s or Plains penstemon, P. fendleri. Fendler’s penstemon blooms April through August from the Oklahoma Panhandle down to Chihuahua and even into eastern Arizona. Soft lavender flowers with purple guidelines grow along the stem over half the length of it. It is “a common plant on the Llano Estacado” (Penstemons, Nold). This species is definitely underused in our gardens, but it isn't large or showy. Would make a good specimen for the rock garden. The species is named for Augustus Fendler, the prolific German plant collector. (Photos left and right from Palo Duro Canyon.)
Some of the many other penstemons, these are blue flowering and pollinated by bees: Penstemon angustifolius, P. versicolor, P. virens, and P. caespitosus, a mat forming penstemon. If you see a penstemon for sale, give it a try.
Penstemons in Mesic Beds
Mesic beds are beds that would need supplemental irrigation of an inch every other week and whose soil is amended with compost. Penstemons prefering mesic conditions combine well with many prairie plants that are used to more rainfall than what the Panhandle receives. A few typical companion plants would include monardas (bee balm), echinaceas, boltonia, obedient plant, hibiscus, salvias, rudbeckia, and roses.
Pineleaf penstemon, Penstemon pinifolius, resides on the borderline between xeric and mesic beds and borders. Mat forming and low growing only 6-10” tall and will spread thrice that size, pineleaf penstemon have evergreen, filiform leaves, similar to pine needles. Narrow tubular orange-red flowers bloom from mid-May to the end of June. There is an equally delicate looking ‘Mersea Yellow’ variety, one of the few penstemons with a yellow bloom. Loose gravelly soils are best in sun or part shade locations. As with all penstemons, the balance between dry and wet soil needs to be mastered for longevity is important here. Mastery of this technique may reward you with an old Penstemon pinifolius with woody stems resembling a bonsai. I have only seen this once, but is known to be shrubby in its native southern New Mexico and eastern Arizona. Dwarf ‘Compactum’ and ‘Luminous’ varieties can be found through Highcountrygardens.com. (Photo left of P. pinifolius and 'Mersea Yellow'.)
Penstemons known as the Mexicali hybrids perform well throughout the summer for a very long bloom period. They are less fussy and longer living too. Penstemon x mexicali ‘Pikes Peak Purple, ‘Red Rocks’, ‘Shadow Mountain’, ‘Windwalker Garnet’ and ‘Carloyn’s Hope’are in the Plant Select program. Another great hybrid is ‘Sweet Joanne’ and is licensed to Blooms of Bressingham. (HortScience, Penstemon ‘Sweet Joanne’.) The leaves are a medium glossy green and the plant is mounding, and somewhat bushy up to 12-15” as they age. There are other x mexicali hybrids, too. (Photo at right is 'Red Rocks', showing dried seed pod and distinctive guidelines.)
Rocky Mountain penstemon, Penstemon strictus, will also grow under mesic conditions in clay soil and part shade. It’s purple-blue flowers over four-six weeks are a welcome addition to the garden. Rocky Mountain penstemon is native to pinyon-juniper woodlands, oak scrub and up to ponderosa pine and spruce-aspen forest in clearings. It’s hard to miss it when hiking in the summer Rockies. (Photo at left.)
Shell or large-flowered penstemon, Penstemon grandiflorus, has done well in our area too. Its native range once extended to Missouri, Wisconsin and Minnesota, as well as the northern plains. Large plant as well as flower, growing 20-40” tall depending on rainfall. 'Prairie Snow' and 'War Axe' are two P. grandiflorus in the GreatPlants releases and introductions.
Another favorite penstemon for mesic beds with average organic content and drainage is the foxglove penstemon, P. cobaea. It requires more than our normal 17 inches of average rainfall, so should do well when paired with more typical water-thirsty plants. Grows natural in calcareous, limestone and sandy soils.
Another species called foxglove penstemon is, of course, Penstemon digitalis ‘Husker Red’, the Perennial Plant of the Year choice for 1996. This penstemon is native in the eastern Great Plains to Maine, New England and into Canada. Native as it is to areas of more moisture and better soils, this penstemon can grow up to five feet tall. P. digitalis is the most tolerant to moisture. The cultivar 'Husker Red' was chosen for its dark red-purple leaves and white flowers with a large corolla sometimes tinged with purple that bloom from April to July. Named after the famed University of Nebraska Cornhuskers “Big Red” football team. (Photo at right.)
Studying the photo of the leaves of 'Husker Red' and compared to the glaucous, narrow, grayish leaves of western penstemons illustrates the difference in water needs. Larger leaves, less protected by tiny hairs (the gray look of dryland penstemons) with a waxy bloom or coating (glaucous) evaporate more water.
Maintenance: Western penstemons are the perfect perennial for area gardens. For the xeric penstemon – the more you leave them alone the better, only needing one inch a month for moisture during drought periods. Good draining soil is a must. Fertilization and amending of soil with organics is not recommended. I’ve read conflicting instructions on deadheading penstemons. The best advice is to dead head the early stems, and leave the later ones on until late winter to early spring. Let the seeds mature on a few stems and spread the seeds around or trade with friends. Care should be taken when watering in the winter not to promote soggy ground.
Penstemons are terrific native wildflowers to choose for beautifully thriving, low maintenance and low water-use gardens. Whether placed in xeric, cactus, native plant or rock gardens, they can hardly be beat for attracting pollinators. For higher water-use areas, try a few of the hybrids, or a use them as the British do, as bedding plants. When making your plant choices, whether it’s planting for hummingbirds, or bees, or by color, or time of bloom, set aside some space to try one of America’s signature plants.
I've done my best to identify the penstemons in these phtos, taken from gardens and in the wild; please pardon me if any of them are incorrectly identified. Robert Nold’s book, Penstemons, was a main reference source for this GardenNotes, as well as the APS website.
Penstemon ‘Sweet Joanne’. HortScience.
Insects that Visit Pentstemon Flowers, Bulletin of the American Penstemon Society Vol. 68, Sarah Kimball and Paul Wilson.
National Gardening Association Plant Data Base, includes extensive list of penstemon species and hybrids with limited photos and information. Hybirds are listed towards the end.
Penstemons, Robert Nold, Timber Press, Portland, 1999. Robert Nold’s book was a main reference source for this GardenNotes.
Passionate Gardening, Good Advice for Passionate Gardening, Pestemons article, Lauren Spring, Fulcrum Press, 2000.
Penstemons: Easty Growing Saviours of the Late Summer Garden, James Alexander-Sinclair, The Guardian, Aug. 21, 2009.
Plants for Natural Gardens, Judith Phillips, Museum of New Mexico Press, Santa Fe, 1995.
Smoke, Seed Germination and Penstemons, Paula. J. Fornwalt, American Penstemon Society Newsletter, Spring, 2015.
Unknown penstemon and rabbit, photo at right.
Angie Hanna, August 15, 2017