Beardtongue

Penstemon /ˈpɛnstɪmən/,^[1] the beardtongues, is a large genus of roughly 280 species of flowering plants native mostly to the Nearctic, but with a few species also found in the North American portion of the Neotropics.^[2] It is the largest genus of flowering plants endemic to North America.^[3][4] As well as being the scientific name, penstemon is also widely used as a common name for all Penstemon species alongside beardtongues.

Formerly placed in the family Scrophulariaceae by the Cronquist system, new genetic research has placed it in the vastly expanded family Plantaginaceae.^[5][6] The total number of species is uncertain due to on going research into if some of the named species are actually subspecies or misidentifications of already identified species.^[7]

Description

A prominent, often hairy, staminode is the most distinctive feature of this genus, as in this Penstemon rupicola flower

Golden-beard Penstemon (Penstemon barbatus)

Penstemon bridgesii

Bellflower Beardtongue (Penstemon campanulatus)

Penstemon confertus

Talus Slope Penstemon (Penstemon digitalis)

Lowbush Penstemon (Penstemon fruticosus)

Davidson's Penstemon (Penstemon davidsonii)

Lilac Penstemon (Penstemon gracilis)

Hairy Beardtongue (Penstemon hirsutus)

Penstemon hirsutus pubescens

Pineneedle Beardtongue (Penstemon pinifolius)

Littleflower Penstemon (Penstemon procerus)

Serrulate Penstemon (Penstemon serrulatus)

Prairie-clover (Penstemon speciosus)

They have opposite leaves,^[8] partly tube-shaped, and two-lipped flowers and seed capsules. The most distinctive feature of the genus is the prominent staminode, an infertile stamen.^[8] The staminode takes a variety of forms in the different species; while it is 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 of "beardtongue".^[8]

Most penstemons form a durable woody stem (a caudex) and have persistent basal leaves, but some are fully deciduous perennials, the remainder being shrubs or subshrubs.^[9]: 7 Heights can range from 10 cm to as much as 3 meters. Along with their variable growth forms the penstemons have highly variable leaves, often with different leaf shapes on different parts of the same plant. Some species have highly reduced needle like leaves and others broad and rounded leaves, with their texture also running the range of hairy to smooth/glaborous.^{[9]: 11 [10]: 38} In the view of penstemon expert Robert Nold the defining evolutionary characteristic of the genus is adaptation to drought, as demonstrated by their numbers and diversity in the interior west of North America.^{[10]: 53–54}

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.^[10]: 19 Although widespread across North America, and found in habitats ranging from open desert to moist forests, and up to the alpine zone,^[9]: 7 they are not typically common within their range.

History

John Mitchell published the first scientific description in 1748; although he only named it as Penstemon, researchers David Way, Peter James, and Robert Nold identify it as P. laevigatus.^{[11][10]: 58–59} 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). The botanist Casimir Schmidel published a description of the species in 1763, and for this reason he is given priority in botanical publication.^{[10]: 58–59} 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.^[12][11]

Although several more species were found in the early 18th century, they continued to be classified in Chelone until 1828 in some publications. The period of 1810 to 1850 increased the number of known species from 4 to 63, as expeditions traveled through Mexico and the western United States, followed by another 100 up to 1900. Though it should be noted not all these species remained classified as Penstemon.^[11]

The American members of the genus were extensively revised by David D. Keck between 1932 and 1957^[12] and Richard Straw did similar work on the Mexican species slightly later.^[11] In 1960 the important book Penstemon Taxonomy was published by American Penstemon Society president Ralph Bennett with the advice of Keck. This book was updated and republished with the Robin Lodewick in 1980 and continued to be an important source of information about the genus through the year 2000.^[11]

Fieldwork in the remote parts of the Great Basin during the 20th century brought the total number of species known to over 270, though some of this total may be errors or now extinct species.^[11]

Penstemon has been subdivided into six subgenera by using anther dehiscence patterns. Subgenera Cryptostemon and Dissecti each contain one species. As traditionally defined subgenus Penstemon contains about 128 species, subgenus Habroanthus contains about 50, subgenus Saccanthera has about 28 species, and subgenus Dasanthera contains nine. Genetic analysis by Andrea D Wolfe et al. indicates that while some of the previously identified subgenera are natural groupings, many are hopelessly confused.^[13]

Horticulture

Although penstemons are among the most attractive native flowers of North America, Europe has traditionally been far more active in their hybridization with hundreds of hybrids developed since the early 19th century. The first offer of seeds for sale as by John Fraser in 1813.^[11] The earliest development is somewhat shrouded in mystery; for instance Flanagan & Nutting's 1835 catalog mentions a 'Penstemon Hybridum' but does not describe it.^[14]

By 1860, a half-dozen French growers are known to have developed hybrids, most notably Victor Lemoine, while in 1857 the German Wilhelm Pfitzer listed 24 varieties. In 1861 the British Royal Horticultural Society held trials in which 78 varieties were entered. The Scottish firm of John Forbes first offered penstemons in 1870, eventually becoming the biggest grower in the world; in 1884 their catalog listed 180 varieties. By 1900 Forbes had offered 550 varieties, while Lemoine had developed nearly 470 by the time of his death in 1911. Few of these have survived to the present day.^[14]

A number of different species have been used in the hybridization process, notably P. cobaea and P. hartwegii.^[14]

The American Penstemon Society was formed in 1946 to promote both horticultural and botanical interest.^[11]

In North America, penstemons are often used in xeriscape landscaping, as many are native to desert or alpine regions and thus quite hardy.^[2] One of the largest collections of penstemons in North America is found at The Arboretum at Flagstaff, Arizona, which hosts a Penstemon Festival each summer.^[15]

Cultivars

The following species and cultivars have gained the Royal Horticultural Society's Award of Garden Merit:-^[16]

Others include 'Dark Towers', developed by Dale Lindgren at the University of Nebraska.^[39]

Species

These 269 species are valid according to both World Flora Online (WFO) and Plants of the World Online (POWO) as of 2023.^[40][41]

• Penstemon abietinus Pennell – Firleaf beardtongue
• Penstemon absarokensis Evert – Absaroka Range beardtongue
• Penstemon acaulis L.O.Williams – Stemless beardtongue
• Penstemon acuminatus Douglas ex Lindl. – Sharpleaf penstemon
• Penstemon alamosensis Pennell & G.T.Nisbet – Los Alamos beardtongue
• Penstemon albertinus Greene – Alberta beardtongue
• Penstemon albidus Nutt. – White penstemon
• Penstemon albomarginatus M.E.Jones – White margin penstemon, whitemargin beardtongue, whitemargin penstemon
• Penstemon ambiguus Torr. – bush penstemon, gilia beardtongue, gilia penstemon
• Penstemon ammophilus N.H.Holmgren & L.M.Schultz – sandloving penstemon
• Penstemon amphorellae Crosswh.
• Penstemon anguineus Eastw. – Siskiyou beardtongue
• Penstemon angustifolius Nutt. ex Pursh – broad-beard beardtongue, broadbeard beardtongue, narrowleaf penstemon
• Penstemon arenarius Greene – Nevada sanddune beardtongue, sanddune penstemon
• Penstemon arenicola A.Nelson – sand penstemon
• Penstemon aridus Rydb. – stiffleaf penstemon
• Penstemon arkansanus Pennell – Arkansas beardtongue
• Penstemon atropurpureus (Sweet) G.Don
• Penstemon attenuatus Douglas – sulphur penstemon
• Penstemon atwoodii S.L.Welsh – Kaiparowits beardtongue
• Penstemon auriberbis Pennell – Colorado beardtongue
• Penstemon australis Small – Eustis Lake beardtongue
• Penstemon azureus Benth. – azure penstemon
• Penstemon baccharifolius Hook. – baccharisleaf beardtongue ^[42]
• Penstemon barbatus (Cav.) Roth – Golden-beard Penstemon or Beardlip penstemon
• Penstemon barnebyi N.H.Holmgren – Barneby's penstemon, White River Valley beardtongue
• Penstemon barrettiae A.Gray – Barrett's beardtongue
• Penstemon bicolor (Brandegee) Clokey & D.D.Keck – pinto beardtongue, pinto penstemon
• Penstemon bleaklyi O'Kane & K.D.Heil
• Penstemon bolanus Straw
• Penstemon bracteatus D.D.Keck – Red Canyon beardtongue
• Penstemon bradburyi Pursh
• Penstemon breviculus (D.D.Keck) G.T.Nisbet & R.C.Jacks. – shortstem beardtongue, shortstem penstemon
• Penstemon brevisepalus Pennell – short-sepaled beardtongue
• Penstemon buckleyi Pennell – buckley penstemon, Buckley's beardtongue
• Penstemon caesius A.Gray – San Bernardino beardtongue
• Penstemon caespitosus Nutt. ex A.Gray – mat penstemon
• Penstemon calcareus Brandegee – limestone beardtongue
• Penstemon californicus (Munz & I.M.Johnst.) D.D.Keck – California penstemon
• Penstemon calycosus Small – longsepal beardtongue
• Penstemon campanulatus (Cav.) Willd. – bellflower beardtongue
• Penstemon canescens Britton – eastern gray beardtongue
• Penstemon cardinalis Wooton & Standl. – cardinal beardtongue
• Penstemon cardwellii Howell – Cardwell's beardtongue
• Penstemon carnosus Pennell – fleshy beardtongue
• Penstemon caryi Pennell – Cary's beardtongue
• Penstemon cedrosensis Krautter
• Penstemon centranthifolius (Benth.) Benth. – scarlet bugler
• Penstemon cinicola D.D.Keck – ash penstemon
• Penstemon clevelandii A.Gray – Cleveland's beardtongue
• Penstemon clutei A.Nelson – Sunset Crater beardtongue, Sunset Crater penstemon
• Penstemon cobaea Nutt. – cobaea beardtongue, Cobaea penstemon
• Penstemon comarrhenus A.Gray – dusty beardtongue, dusty penstemon
• Penstemon concinnus D.D.Keck – Tunnel Springs beardtongue, Tunnel Springs penstemon
• Penstemon confertus Douglas – yellow penstemon
• Penstemon confusus M.E.Jones – Owens Valley beardtongue, Owens Valley penstemon
• Penstemon crandallii A.Nelson – Crandall's beardtongue
• Penstemon cusickii A.Gray – Cusick's beardtongue
• Penstemon cyananthus Hook. – Wasatch beardtongue
• Penstemon cyaneus Pennell – blue penstemon
• Penstemon cyanocaulis Payson – bluestem beardtongue
• Penstemon cyathophorus Rydb. – Northpark penstemon, sagebrush beardtongue
• Penstemon dasyphyllus A.Gray – Cochise beardtongue, purple penstemon
• Penstemon davidsonii Greene – Davidson's penstemon, timberline penstemon
• Penstemon deamii Pennell – Deam's beardtongue
• Penstemon deaveri Crosswh. – Mt. Graham beardtongue
• Penstemon debilis O'Kane & J.L.Anderson – Parachute beardtongue
• Penstemon degeneri Crosswh. – Degener's beardtongue
• Penstemon deustus Douglas ex Lindl. – scabland penstemon
• Penstemon digitalis Nutt. ex Sims – talus slope penstemon, foxglove beardtongue
• Penstemon diphyllus Rydb. – twoleaf beardtongue
• Penstemon discolor D.D.Keck – Catalina beardtongue
• Penstemon dissectus Elliott – dissected beardtongue
• Penstemon distans N.H.Holmgren – Mt. Tumbull beardtongue
• Penstemon dolius M.E.Jones – Jones's penstemon, Jones' beardtongue
• Penstemon duchesnensis (N.H.Holmgren) Neese
• Penstemon eatonii A.Gray – Eaton penstemon, Eaton's penstemon, firecracker penstemon
• Penstemon elegantulus Pennell – rockvine penstemon
• Penstemon ellipticus J.M.Coult. & Fisher – rocky ledge penstemon
• Penstemon erianthera Fraser ex Nutt. – fuzzytongue penstemon
• Penstemon euglaucus English – glaucous beardtongue
• Penstemon eximius D.D.Keck – unusual beardtongue
• Penstemon fasciculatus A.Gray
• Penstemon fendleri Torr. & A.Gray – fendler penstemon, Fendler's beardtongue, Fendler's penstemon
• Penstemon filiformis (D.D.Keck) D.D.Keck – Keck threadleaf beardtongue
• Penstemon filisepalis Straw
• Penstemon flavescens Pennell – high mountain penstemon
• Penstemon floribundus Danley – Cordillia's beardtongue, Cordillia's penstemon
• Penstemon floridus Brandegee – Panamint beardtongue, Panamint penstemon
• Penstemon flowersii Neese & S.L.Welsh – Flowers' beardtongue
• Penstemon franklinii S.L.Welsh – Franklin's penstemon
• Penstemon fremontii Torr. & A.Gray – Fremont penstemon, Fremont's beardtongue
• Penstemon fruticiformis Coville – Death Valley beardtongue, Death Valley penstemon
• Penstemon fruticosus (Pursh) Greene – Greene bush penstemon
• Penstemon gairdneri Hook. – Gairdner's beardtongue
• Penstemon galloensis G.L.Nesom
• Penstemon gentianoides (Kunth) Poir.
• Penstemon gentryi Standl.
• Penstemon gibbensii Dorn – Gibbens' beardtongue
• Penstemon glaber Pursh – sawsepal penstemon, western smooth beardtongue
• Penstemon glandulosus Douglas ex Lindl. – stickystem penstemon
• Penstemon glaucinus Pennell – blueleaf beardtongue
• Penstemon globosus (Piper) Pennell & D.D.Keck – globe penstemon
• Penstemon goodrichii N.H.Holmgren – Lapoint beardtongue
• Penstemon gormanii Greene – Gorman's beardtongue
• Penstemon gracilentus A.Gray – slender penstemon
• Penstemon gracilis Nutt. – lilac penstemon, slender penstemon
• Penstemon grahamii D.D.Keck – Uinta Basin beardtongue
• Penstemon griffinii A.Nelson – Griffin's beardtongue
• Penstemon grinnellii Eastw. – Grinnell's beardtongue
• Penstemon guadalupensis A.Heller – Guadalupe beardtongue
• Penstemon hallii A.Gray – Hall's beardtongue
• Penstemon harbourii A.Gray – Harbour's beardtongue
• Penstemon harringtonii Penland – Harrington's beardtongue
• Penstemon hartwegii Benth. – Hartweg's beardtongue
• Penstemon havardii A.Gray – Big Bend beardtongue
• Penstemon haydenii S.Watson ex J.M.Coult. – blowout beardtongue, blowout penstemon
• Penstemon henricksonii Straw
• Penstemon heterodoxus A.Gray – Sierra beardtongue, Sierra penstemon
• Penstemon heterophyllus Lindl. – bunchleaf penstemon
• Penstemon hidalgensis Straw
• Penstemon hirsutus (L.) Willd. – hairy beardtongue
• Penstemon humilis Nutt. ex A.Gray – low beardtongue, low penstemon
• Penstemon imberbis (Kunth) Trautv.
• Penstemon immanifestus N.H.Holmgren – Steptoe Valley beardtongue, Steptoe Valley penstemon
• Penstemon incertus Brandegee – Mojave beardtongue
• Penstemon inflatus Crosswh. – inflated beardtongue
• Penstemon isophyllus B.L.Rob.
• Penstemon jamesii Benth. – James penstemon, James' beardtongue
• Penstemon janishiae N.H.Holmgren – Antelope Valley beardtongue, Janish's penstemon
• Penstemon kingii S.Watson – King's beardtongue, King's penstemon
• Penstemon kralii D.Estes
• Penstemon labrosus (A.Gray) Mast. ex Hook.f. – San Gabriel beardtongue
• Penstemon laetus A.Gray – mountain blue penstemon
• Penstemon laevigatus Aiton – eastern smooth beardtongue
• Penstemon laevis Pennell – southwestern beardtongue, southwestern penstemon
• Penstemon lanceolatus Benth.
• Penstemon laricifolius Hook. & Arn. – larchleaf beardtongue
• Penstemon laxiflorus Pennell – nodding beardtongue
• Penstemon laxus A.Nelson – tufted penstemon
• Penstemon leiophyllus Pennell – smoothleaf beardtongue, smoothleaf penstemon
• Penstemon lemhiensis (D.D.Keck) D.D.Keck & Cronquist – Lemhi penstemon
• Penstemon lentus Pennell – handsome beardtongue, handsome penstemon
• Penstemon leonardii Rydb. – Leonard's beardtongue, Leonard's penstemon
• Penstemon leonensis Straw
• Penstemon linarioides A.Gray – creeping penstemon, toadflax penstemon
• Penstemon longiflorus (Pennell) S.L.Clark – longflower penstemon
• Penstemon luteus G.L.Nesom
• Penstemon lyallii (A.Gray) A.Gray – Lyall's beardtongue
• Penstemon marcusii (D.D.Keck) N.H.Holmgren – Marcus' beardtongue
• Penstemon mensarum Pennell – tiger beardtongue
• Penstemon metcalfei Wooton & Standl. – Metcalfe's beardtongue
• Penstemon miniatus Lindl.
• Penstemon miser A.Gray – Malheur penstemon
• Penstemon moffatii Eastw. – Moffatt's beardtongue
• Penstemon mohinoranus Straw
• Penstemon monoensis A.Heller – Mono penstemon
• Penstemon montanus Greene – cordroot beardtongue
• Penstemon moriahensis N.H.Holmgren – Mount Moriah penstemon, Mt. Moriah beardtongue
• Penstemon mucronatus N.H.Holmgren
• Penstemon multiflorus (Benth.) Chapm. ex Small – manyflower beardtongue
• Penstemon murrayanus Hook. – scarlet beardtongue
• Penstemon nanus D.D.Keck – dwarf beardtongue
• Penstemon navajoa N.H.Holmgren – Navajo Mountain beardtongue
• Penstemon neomexicanus Wooton & Standl. – New Mexico beardtongue
• Penstemon neotericus D.D.Keck – Plumas County beardtongue

Penstemon newberryi, Yosemite National Park, 2005

• Penstemon newberryi A.Gray – mountain pride, pride-of-the-mountains
• Penstemon nitidus Douglas ex Benth. – waxleaf penstemon
• Penstemon nudiflorus A.Gray – Flagstaff beardtongue
• Penstemon occiduus Straw
• Penstemon oklahomensis Pennell – Oklahoma beardtongue, Oklahoma penstemon
• Penstemon oliganthus Wooton & Standl. – Apache beardtongue
• Penstemon ophianthus Pennell – Arizona beardtongue, coiled anther penstemon
• Penstemon osterhoutii Pennell – Osterhout's beardtongue
• Penstemon ovatus Douglas – eggleaf beardtongue
• Penstemon pachyphyllus A.Gray ex Rydb. – thickleaf beardtongue, thickleaf penstemon
• Penstemon pahutensis N.H.Holmgren – Pahute penstemon, Paiute beardtongue
• Penstemon pallidus Small – pale beardtongue
• Penstemon palmeri A.Gray – Palmer's penstemon, Palmer penstemon
• Penstemon papillatus J.T.Howell – Inyo beardtongue
• Penstemon parryi A.Gray – Gray Parry penstemon, Parry's beardtongue
• Penstemon parvulus (A.Gray) Krautter – Aquarius Plateau beardtongue
• Penstemon parvus Pennell
• Penstemon patens (M.E.Jones) N.H.Holmgren – Lone Pine beardtongue, Lone Pine penstemon
• Penstemon payettensis A.Nelson & J.F.Macbr. – Payette beardtongue
• Penstemon paysoniorum D.D.Keck – Payson's beardtongue
• Penstemon peckii Pennell – Peck's beardtongue
• Penstemon penlandii W.A.Weber – penland beardtongue, Penland's beardtongue
• Penstemon pennellianus D.D.Keck – Blue Mountain beardtongue
• Penstemon perfoliatus Al.Brongn.
• Penstemon perpulcher A.Nelson – Minidoka beardtongue
• Penstemon personatus D.D.Keck – closethroat beardtongue
• Penstemon petiolatus Brandegee – lime penstemon, petiolate beardtongue
• Penstemon pinifolius Greene – pineneedle beardtongue, pineneedle penstemon
• Penstemon pinorum L.M.Shultz & J.S.Shultz – Pine Valley penstemon
• Penstemon plagapineus Straw
• Penstemon platyphyllus Rydb. – broadleaf beardtongue, broadleaf penstemon
• Penstemon potosinus Straw
• Penstemon pratensis Greene – whiteflower beardtongue, western whiteflower penstemon
• Penstemon procerus Douglas ex Graham – littleflower penstemon, pincushion beardtongue
• Penstemon pruinosus Douglas – Chelan beardtongue
• Penstemon pseudoparvus Crosswh. – Mt. Washington beardtongue, San Mateo penstemon
• Penstemon pseudoputus (Crosswh.) N.H.Holmgren – Kaibab Plateau beardtongue
• Penstemon pseudospectabilis M.E.Jones – desert penstemon
• Penstemon pudicus Reveal & Beatley – bashful penstemon, Kawich Range beardtongue
• Penstemon pumilus Nutt. – Salmon River beardtongue
• Penstemon punctatus Brandegee
• Penstemon purpusii Brandegee – Snow Mountain beardtongue
• Penstemon putus A.Nelson – Black River beardtongue
• Penstemon radicosus A.Nelson – matroot penstemon
• Penstemon rattanii A.Gray – Rattan's beardtongue
• Penstemon richardsonii Douglas ex Lindl. – cutleaf beardtongue
• Penstemon roezlii Regel – Roezl's penstemon
• Penstemon roseus (Cerv. ex Sweet) G.Don
• Penstemon rostriflorus Kellogg – beaked beardtongue, beakflower penstemon, Bridge penstemon
• Penstemon rotundifolius A.Gray
• Penstemon rubicundus D.D.Keck – Wassuck penstemon, Wassuk Range beardtongue
• Penstemon rupicola (Piper) Howell – cliff beardtongue
• Penstemon rydbergii A.Nelson – meadow beardtongue, Rydberg penstemon, Rydberg's penstemon
• Penstemon saltarius Crosswh.
• Penstemon saxosorum Pennell – upland beardtongue
• Penstemon scapoides D.D.Keck – pinyon beardtongue
• Penstemon scariosus Pennell – White River beardtongue
• Penstemon schaffneri (Hemsl.) Straw
• Penstemon secundiflorus Benth. – sidebells penstemon
• Penstemon seorsus (A.Nelson) D.D.Keck – shortlobe penstemon
• Penstemon sepalulus A.Nelson – littlecup beardtongue
• Penstemon serrulatus Menzies ex Sm. – serrulate penstemon
• Penstemon smallii A.Heller – Small's beardtongue
• Penstemon spatulatus Pennell
• Penstemon speciosus Douglas – prairie-clover, royal penstemon
• Penstemon spectabilis Thurb. ex A.Gray – showy penstemon
• Penstemon stenophyllus A.Gray – Sonoran beardtongue
• Penstemon stephensii Brandegee – Stephens' penstemon
• Penstemon strictiformis Rydb. – Mancos penstemon, stiff penstemon
• Penstemon strictus Benth. – Rocky Mountain beardtongue, Rocky Mountain penstemon
• Penstemon subglaber Rydb. – smooth penstemon
• Penstemon subserratus Pennell – finetooth beardtongue
• Penstemon subulatus M.E.Jones – hackberry beardtongue
• Penstemon sudans M.E.Jones – Susanville beardtongue, Susanville penstemon
• Penstemon superbus A.Nelson – superb beardtongue
• Penstemon tenuiflorus Pennell – eastern whiteflower beardtongue
• Penstemon tenuifolius Benth.
• Penstemon tenuis Small – sharpsepal beardtongue
• Penstemon tepicensis Straw
• Penstemon teucrioides Greene – germander beardtongue
• Penstemon thompsoniae (A.Gray) Rydb. – Thompson's penstemon, Thompson's beardtongue, Thompson penstemon
• Penstemon thurberi Torr. – Thurber's penstemon, Thurber penstemon
• Penstemon tidestromii Pennell – Tidestrom's beardtongue
• Penstemon tracyi D.D.Keck – Trinity penstemon
• Penstemon triflorus A.Heller – Heller's beardtongue
• Penstemon triphyllus Douglas – Riggin's penstemon
• Penstemon tubaeflorus Nutt. – white wand beardtongue
• Penstemon uintahensis Pennell – Uinta Mountain beardtongue
• Penstemon utahensis Eastw. – Utah penstemon
• Penstemon venustus Douglas – Venus penstemon
• Penstemon virens Pennell ex Rydb. – Front Range beardtongue
• Penstemon virgatus A.Gray – upright blue beardtongue
• Penstemon vizcainensis Moran
• Penstemon vulcanellus Crosswh.
• Penstemon wardii A.Gray – Ward's beardtongue
• Penstemon washingtonensis D.D.Keck – Washington beardtongue
• Penstemon watsonii A.Gray – Watson's penstemon, Watson's beardtongue, Watson penstemon
• Penstemon wendtiorum B.L.Turner^[43]
• Penstemon whippleanus A.Gray – dark beardtongue, Whipple's penstemon
• Penstemon wilcoxii Rydb. – Wilcox's penstemon
• Penstemon wislizeni (A.Gray) Straw
• Penstemon wrightii Hook. – Wright's beardtongue
• Penstemon yampaensis Penland – Yampa beardtongue

Natural hybrids

These five naturally occurring hybrids are valid according to WFO and POWO.^[40][41]

• Penstemon × crideri A.Nelson – Crider penstemon, Crider's penstemon
• Penstemon × dubius Davidson – dubius penstemon
• Penstemon × mirus A.Nelson
• Penstemon × parishii A.Gray
• Penstemon × peirsonii Munz & I.M.Johnst.

Ambiguous species

These 35 species and two natural hybrids are of uncertain validity. Twenty-seven are recognized as valid by either WFO or POWO, but not both.^[40][41] The USDA Natural Resources Conservation Service PLANTS database (PLANTS) uses eight species not recognized by either WFO or POWO.^[44]

• Penstemon alluviorum Pennell^[45][46] – lowland beardtongue
• Penstemon angelicus (I.M.Johnst.) Moran
• Penstemon brandegeei (Porter) Rydb.
• Penstemon brevibarbatus Crosswhite
• Penstemon bryantiae^[47] D.D. Keck
• Penstemon cerrosensis Kellogg
• Penstemon compactus (D.D.Keck) Crosswh.^[48] – compact penstemon
• Penstemon curtiflorus (D.D.Keck) N.H.Holmgren
• Penstemon dugesii Pérez-Calix & Zacarías
• Penstemon grandiflorus^[49] Nutt. – large beardtongue, largeflowered penstemon
• Penstemon hesperius M.E.Peck
• Penstemon idahoensis N.D.Atwood & S.L.Welsh^[50][51] – Idaho beardtongue
• Penstemon jaliscensis B.L.Rob.
• Penstemon jonesii Pennell^[a] – Jones' penstemon
• Penstemon laevigatus Soland.
• Penstemon leptanthus Pennell^[52][53] – Sevier Plateau beardtongue
• Penstemon minutifolius Straw
• Penstemon moronensis Crosswh.^[b]
• Penstemon parishii A.Gray – Parish's penstemon
• Penstemon parviflorus Pennell^[54] – Montezuma County beardtongue
• Penstemon reidmoranii Zacarías & A.Wolfe
• Penstemon ramosus Crosswh.^[55][56] – lanceleaf beardtongue, lanceleaf penstemon
• Penstemon retrorsoides Crosswh. – Adobe Hills beardtongue
• Penstemon retrorsus Payson^[57]
• Penstemon rhizomatosus N.H.Holmgren^[58][59]
• Penstemon salmonensis N.H.Holmgren
• Penstemon spathulatus Eastw. ex C.F.Baker – Wallowa beardtongue
• Penstemon tiehmii N.H.Holmgren^[60][61] – Tiehm's beardtongue
• Penstemon tubiflorus Nutt.
• Penstemon tusharensis Penstemon tusharensis N.H.Holmgren^[62][63] – Tushar Range beardtongue
• Penstemon unilateralis Rydb.^[64]
• Penstemon versicolor Pennell^[65]
• Penstemon xylus A.Nelson
• Penstemon × jonesii Pennell^[66][a]
• Penstemon × moronensis Crosswh.^[b]

See also

• HMS Pentstemon

References