{{Short description|Plant species in the veronica family}} {{Speciesbox | image = Penstemon whippleanus.jpg | image_alt = | image_caption = Inflorescence with many dark flowers | status = {{TNCStatus}} | status_system = TNC | status_ref = {{sfn|NatureServe 2025}} | genus = Penstemon | species = whippleanus | authority = A.Gray | synonyms_ref = {{sfn|POWO 2025}} | synonyms = {{Species list | Penstemon arizonicus | | Penstemon pallescens | | Penstemon stenosepalus | }} }}

'''''Penstemon whippleanus''''', commonly known as '''dusky penstemon''' or '''Whipple's penstemon''', is a summer blooming perennial flower in the large ''Penstemon'' genus. It is a widespread plant within the hemiboreal forests of the Rocky Mountains in North America. It is noted for the large deep purple-red flowers and a preference for high mountain elevations.{{sfn|Denver Botanic Gardens|2018|p=182}}

==Description== thumb|left|Detail of ''P. whippleanus'' in bloom showing highly glandular petals Dusky penstemon is easily recognizable because it is the only species with its combination of large flower size, striking dark or pale flower, and the height of its flowering stems.{{sfn|Denver Botanic Gardens|2018|p=182}} They are usually 20 to 65 centimeters tall, but on occasion may be as short as 8 cm or as tall as 1 meter.{{sfn|Freeman 2020}}

Like most members of its genus, ''Penstemon whippleanus'' is an evergreen perennial plant. They have both basal leaves, leaves attached to the base of the plant, and in pairs on opposite sides of their flowering stems. The basal leaves grow on short stems, are smooth without hairs, but not leathery. Each basal leaf is about 40–90 mm long and 10–30 mm wide with a generally blade ovate to lanceolate shape. The leaves on the flowering stems are generally narrower and shorter, 25–60 mm in length and 3–15 mm, with a blade lanceolate to oblanceolate shape.{{sfn|Freeman 2020}}

The flowering stem are tall and generally straight with multiple flowers clustered at nodes just above each pair of leaves. The flowering stem grow indeterminately{{sfn|Freeman 2020}} and are smooth (glabrous) below and glandular and hairy above.{{sfn|Ackerfield|2015|p=596}} Each flower cluster has two groupings (a cyme) with 2-4 flowers, 4-8 in total. The bracts near attachment point are lanceolate.{{sfn|Freeman 2020}}

The flowers are large, usually 20–27 mm in length and occasionally up to 30 mm in length with a width of 8–10 mm at the mouth.{{sfn|Freeman 2020}} The flowers are most often a gothic black purple, but also can be violet, blue, and creamy white.{{sfn|Denver Botanic Gardens|2018|p=182}} The white form of the flower is mostly found in the mountains in the Great Basin and on Colorado's Grand Mesa and does not have an intermediate form with darker specimens.{{sfn|Cronquist et al. 1984|p=398}}{{sfn|Schneider|2024}} The flowers have fine lines inside the mouth of the flower that serve as nectar guides, white or lavender colored in dark forms of the flower and purple in light colored forms.{{sfn|Freeman 2020}} The lower lip of the flower tube also has noticeable long white hairs.{{sfn|Denver Botanic Gardens|2018|p=182}}

thumb|right|Penstemon whippleanus seed capsules The seed capsules are rounded with four lobes and stretching upwards to a sharp tip at the top of each lobe. Split open each capsule holds numerous seeds. The seeds require a 6 to 12 week cold stratification for good germination.{{sfn|Love|n.d.}}

==Taxonomy== ''Penstemon whippleanus'' was named and described by the famous American botanist Asa Gray in Proceedings of the American Academy of Arts and Sciences in 1862.{{sfn|WFO 2025e}}{{sfn|POWO 2025}} He described it from a specimen collected by Dr. John Milton Bigelow made in October 1853 in the Sandia Mountains of New Mexico.{{sfn|Gray|1862|p=73}} In the same issue he inadvertently described another specimen of ''P.&nbsp;whippleanus'' collected in Colorado by Charles Christopher Parry as ''Penstemon glaucus'' var. ''stenosepalus''.{{sfn|WFO 2025b}}{{sfn|Gray|1862|p=70}} In 1899 another collection was incorrectly described as a new species, ''Penstemon arizonicus'', by Amos Arthur Heller in the Bulletin of the Torrey Botanical Club.{{sfn|WFO 2025a}} American botanist Thomas J. Howell reclassified Asa Gray's variety of ''P.&nbsp;glaucus'' as ''Penstemon stenosepalus'' in his book ''A Flora of northwest America'' in 1901.{{sfn|WFO 2025d}} Another specimen from Rabbit Ears Pass Colorado was described as ''Penstemon pallescens'' by George E. Osterhout in 1930.{{sfn|WFO 2025c}}<ref>{{cite journal |last1=Osterhout |first1=George E. |title=New Plants From Colorado |journal=Bulletin of the Torrey Botanical Club |date=November 1930 |volume=57 |issue=8 |pages=559–560 |url=https://archive.org/details/sim_journal-of-the-torrey-botanical-society_1930-11_57_8/page/560/mode/2up |access-date=21 January 2023 |publisher=Torrey Botanical Society |doi=10.2307/2480672 |jstor=2480672 |language=English}}</ref>

In 1920 Francis W. Pennell reevaluated Asa Gray's identification of the specimen collected near the headwaters of Clear Creek as ''P.&nbsp;glaucus'' var. ''stenosephalus'' and Howell's description of it as ''P.&nbsp;stenosephalus'' and instead identified it as ''P.&nbsp;whippleanus'' despite the color variations across its range.<ref>{{cite journal |last1=Pennell |first1=Francis W. |title=Scrophulariaceae of the Central Rocky Mountain States |journal=Contributions from the United States National Herbarium |date=1920 |volume=20 |issue=9 |pages=376–377 |url=https://repository.si.edu/handle/10088/26992?show=full |publisher=Smithsonian Institution |hdl=10088/26992?show=full |language=EN}}</ref> The respected ''Penstemon'' expert David D. Keck agreed with this in his article "Studies in Penstemon VIII" published in 1945 and additionally reevaluated the identification of ''P.&nbsp;arizonicus'' and ''P.&nbsp;pallescens'' as species, establishing their currently accepted status as synonyms for ''P.&nbsp;whippleanus''.<ref>{{cite book |last1=Bennett |first1=Ralph W. |title=Penstemon Nomenclature |date=1987 |publisher=American Penstemon Society |location=Eugene, Oregon |pages=16, 20, 24, 41, 54, 68 |edition=2nd}}</ref>

{|class="wikitable sortable mw-collapsible" id="Synonyms" |+ class="nowrap" | Table of Synonyms{{sfn|POWO 2025}} ! Name ! Year ! Rank |- | ''Penstemon arizonicus'' {{small|A.Heller}} | 1899 |data-sort-value=A | species |- | ''Penstemon glaucus'' var. ''stenosepalus'' {{small|A.Gray}} | 1862 |data-sort-value=D | variety |- | ''Penstemon pallescens'' {{small|Osterh.}} | 1930 |data-sort-value=A | species |- | ''Penstemon stenosepalus'' {{small|(A.Gray) Howell}} | 1901 |data-sort-value=A | species |}

===Names=== thumb|right|Near the Lofty Lake, High Uinta, Utah Asa Gray named ''Penstemon whippleanus'' in honor of the leader of one of the two southern Pacific Railroad Surveys, Lt. Amiel Weeks Whipple.{{sfn|Gray|1862|p=73}}{{sfn|Heil et al. 2013|p=724}} It is known by the related common names ''dusky penstemon'' and ''dusky beardtongue''.{{sfn|Heflin|1997|p=45}}{{sfn|Heil et al. 2013|p=724}} From its scientific namesake it is also called ''Whipple's penstemon'',{{sfn|Denver Botanic Gardens|2018|p=182}} ''Whipple's beardtongue'',{{sfn|Freeman 2020}} and rarely ''Whipplean penstemon''.{{sfn|Young|Young|1984|p=196}}

==Range and habitat== ''Penstemon whippleanus'' is widely distributed in the central Rocky Mountains of North America. It is recorded by the USDA Natural Resources Conservation Service PLANTS database (PLANTS) as growing in New Mexico, Arizona, Colorado, Utah, Wyoming, Idaho, and Montana. However, there are no county level distributions for Montana recorded in the PLANTS database.{{sfn|NRCS 2025}}

''Penstemon whippleanus'' grows primarily in the subalpine or subarctic biome from 2500–3600&nbsp;meters with occasional populations above timberline or in foothills as low as 1825&nbsp;meters.{{sfn|Cronquist et al. 1984|p=398}}{{sfn|Love|n.d.}} The plants are generally found on open slopes, meadows, rocky ledges, mountain tundra, and openings in woodlands.<ref name="ColoExtention" />{{sfn|Denver Botanic Gardens|2018|p=182}} They will also readily colonize the gravelly edges of roads and highways;{{sfn|Young|Young|1984|p=196}} the plants have a noted preference for rocky soils.<ref name="Plant Palette" />

===Conservation=== The global status of the dusky penstemon was last reviewed by NatureServe in 1984. At that time they evaluated it as secure (G5). At the state level they only evaluated it in Wyoming, where they thought it was apparently secure (S4) and in Montana, rated as imperiled (S3).{{sfn|NatureServe 2025}}

==Ecology== Alongside other mountain species such as rosy paintbrush (''Castilleja rhexiifolia'') and scarlet paintbrush (''Castilleja miniata''), the dusky penstemon is a host for the geranium plume moth (''Amblyptilia pica'').{{sfn|McCoy|Stermitz|1983|p=902}} The geranium plum moth caterpillars, when presented with both leaves and flowers of the dusky penstemon, chose only the flowers. The flowers contain significant amounts of boschniakine, an alkaloid whereas the leaves only contain trace amounts. The flowers also contain a pyridine named pedicularine and 4-noractinidine.{{sfn|McCoy|Stermitz|1983|p=904}} The 1983 detection of alkaloids in the species as the first in a penstemon, the iridoids being much better known until then.{{sfn|McCoy|Stermitz|1983|p=905}}

==Cultivation== thumb|left|Copenhagen University Botanical Garden Dusky penstemons are planted in gardens as an ornamental plant for their large and striking flowers that appear in summer at high elevations or as early as April in low elevations.<ref name="GrowingPenstemons" /> It is very winter hardy, recorded as surviving in USDA zones 4-8 and a UK hardiness of H4.<ref name="ShootGardening">{{cite web |title=Penstemon whippleanus Whipple's Whipple's beardtongue Care Plant Varieties & Pruning Advice |url=https://www.shootgardening.co.uk/plant/penstemon-whippleanus |website=Shoot Gardening.co.uk |access-date=24 January 2023 |language=en}}</ref><ref name="FineGardening">{{cite web |title=Whipple's penstemon |url=https://www.finegardening.com/plant/whipples-penstemon-penstemon-whippleanus |website=FineGardening |publisher=Taunton Press |access-date=25 January 2023}}</ref> In garden conditions they grow in neutral to acid soils and spread rapidly; they are also tolerant of propagation by division.<ref name="GrowingPenstemons" />

In the garden they are, like most members of the genus, drought tolerant but intolerant of poorly draining soils or waterlogged conditions. They are more tolerant of moisture than most of the genus.<ref name="ColoExtention">{{cite web |last1=Shonle |first1=I. |last2=Vickerman |first2=L.G. |last3=Klett |first3=J.E. |title=Native Herbaceous Perennials for Colorado Landscapes - 7.242 |url=https://extension.colostate.edu/topic-areas/yard-garden/native-herbaceous-perennials-for-colorado-landscapes-7-242/ |website=Colorado State Extension |publisher=Colorado State University |access-date=25 January 2023}}</ref> They are not demanding of rich soils or fertilization, but do produce more flowers in richer soils.<ref name="Plant Palette">{{cite book |last1=Meyer |first1=Susan E |title=''The Plant Palette. Landscaping on the New Frontier: Waterwise Design for the Intermountain West'' |date=2009 |publisher=University Press of Colorado |page=185 |doi=10.2307/j.ctt4cgn94.12 |url=https://doi.org/10.2307/j.ctt4cgn94.12 |access-date=25 January 2023}}</ref> Because of its native habitat ''P.&nbsp;whippleanus'' is particularly suited to higher elevation gardens.<ref>{{cite web |last1=Henson |first1=Y. |last2=Langelo |first2=L. |title=Growing Penstemons - 7.428 |url=https://extension.colostate.edu/topic-areas/yard-garden/growing-penstemons-7-428/ |website=Colorado State Extension |publisher=Colorado State University |access-date=25 January 2023 |date=February 2021}}</ref>

Dusky penstemon grows in full sun and partial shade, but are healthier in warmer climates with afternoon shade. They are resistant to browsing by deer,<ref name="FineGardening" /> but young plants in garden settings are often damaged by eleworms, slugs, or snails.<ref name="ShootGardening" /> They are also vulnerable in garden settings to powdery mildew, rust, leaf spots, and Southern blight.<ref name="FineGardening" /> Their seeds require cold and moist stratification of three months for good germination rates or to be planted outside over the winter with a similar period of cold conditions.<ref name="GrowingPenstemons">{{cite book |last1=Lindgren |first1=Dale T. |title=Growing penstemons : species, cultivars, and hybrids |date=2003 |publisher=Infinity Pub |location=Haverford, PA |isbn=0741415291 |pages=93–94}}</ref>

==See also== * List of ''Penstemon'' species

==Gallery==

<gallery class="center"> Image:P whippleanus Detail Mogollon Mtns Bursum Road Aug 5 2007.jpg|Penstemon whippleanus Mogollon Mtns., Bursum Road, Aug. 5, 2007. photo courtesy Dale A. Zimmerman Herbarium </gallery>

==References== ===Citations=== {{Reflist}}

===Sources=== ;Books {{Refbegin}} * {{Cite book |last1=Ackerfield |first1=Jennifer |date=2015 |title=Flora of Colorado |language=en |edition=First |location=Fort Worth, Texas |publisher=Botanical Research Institute of Texas Press |isbn=978-1-889878-45-4 |oclc=910162216}} * {{Cite book |last1=Cronquist |first1=Arthur |author-link1=Arthur Cronquist |last2=Holmgren |first2=Arthur H. |last3=Holmgren |first3=Noel H. |last4=Reveal |first4=James L. |author-link4=James L. Reveal |last5=Holmgren |first5=Patricia K. |author-link5=Patricia Kern Holmgren |date=1984 |title=Intermountain Flora : Vascular Plants of the Intermountain West, U.S.A. |url=https://archive.org/details/intermountainflo0000unse |url-access=registration |language=en |volume=Four. Subclass Asteridae (except Asteraceae) |location=New York |publisher=Published for the New York Botanical Garden by Hafner Pub. Co. |isbn=978-0-89327-248-7 |oclc=320442 |access-date=5 October 2025 |ref={{sfnref|Cronquist et al. 1984}}}} * {{Cite book |last1=Denver Botanic Gardens |date=2018 |title=Wildflowers of the Rocky Mountain region |location=Portland, Oregon |publisher=Timber Press |isbn=9781604696448 |oclc=1030444975}} * {{Cite book |last1=Heflin |first1=Jean |date=1997 |title=Penstemons : The Beautiful Beardtongues of New Mexico |url=https://archive.org/details/penstemonsbeauti0000hefl/page/20 |url-access=registration |language=en |location=Albuquerque, New Mexico |publisher=Jackrabbit Press |isbn=978-0-9659693-0-7 |oclc=39050925 |access-date=5 October 2025}} * {{Cite book |last1=Heil |first1=Kenneth D. |last2=O'Kane |first2=Steve L. Jr. |last3=Reeves |first3=Linda Mary |last4=Clifford |first4=Arnold |date=2013 |title=Flora of the Four Corners Region: Vascular Plants of the San Juan River Drainage, Arizona, Colorado, New Mexico, and Utah |url=https://archive.org/details/mobot31753003888887 |language=en |edition=First |location=St. Louis, Missouri |publisher=Missouri Botanical Garden |isbn=978-1-930723-84-9 |issn=0161-1542 |lccn=2012949654 |oclc=859541992 |access-date=5 October 2025 |ref={{sfnref|Heil et al. 2013}}}} * {{Cite book |last1=Young |first1=Robert Glen |last2=Young |first2=Joann W. |date=1984 |title=Colorado West : Land of Geology and Wildflowers |url=https://archive.org/details/coloradowestland00youn |url-access=registration |location=Grand Junction, Colorado |publisher=R.G. Young |isbn=978-0-9611010-0-8 |oclc=12639106 |access-date=5 October 2025}} {{Refend}}

;Journals {{Refbegin}} * {{Cite journal |last1=Gray |first1=Asa |author-link1=Asa Gray |date=14 October 1862 |title=Five Hundred and Thirteenth Meeting. October 14, 1862. Monthly Meeting; Characters of Some New or Obscure Species of Plants, of Monopetalous Orders, in the Collection of the United States South Pacific Exploring Expedition under Captain Charles Wilkes, U. S. N. with Various Notes and Remarks; Additional Note on the Genus ''Rhytidandra''; Synopsis of the Genus ''Pentstemon''; Revision of the North American Species of the Genus. ''Calamagrostis'', Sect. Deycuxia |url=https://www.biodiversitylibrary.org/page/3097342 |journal=Proceedings of the American Academy of Arts and Sciences |volume=6 |pages=36–81 |doi=10.2307/20179494 |doi-access=free |jstor=20179494 |jstor-access=free |access-date=17 January 2023}} * {{Cite journal |last1=McCoy |first1=Jeff W. |last2=Stermitz |first2=Frank R. |date=November 1983 |title=Alkaloids From Castilleja miniata and Penstemon whippleanus, Two Host Species For the Plume Moth, Amblyptilia (Platyptilia) pica |url=https://d.docecity.com/alkaloids-from-castilleja-miniata-and-penstemon-whippleanus--5f10685c8cdce.html |journal=Journal of Natural Products |volume=46 |issue=6 |pages=902–907 |doi=10.1021/NP50030A012 |access-date=5 October 2025}} {{Refend}}

;Web sources {{Refbegin}} * {{Cite web <!--Deny Citation Bot-->|last1=Freeman |first1=Craig C. |date=5 November 2020 |orig-date=In print 2019 |url=https://floranorthamerica.org/Penstemon_whippleanus |title=''Penstemon whippleanus'' |website=Flora of North America |page=227 |language=en |isbn=978-0-19-086851-2 |oclc=1101573420 |access-date=17 January 2023 |url-status=live |archive-url=https://web.archive.org/web/20251005191337/https://floranorthamerica.org/Penstemon_whippleanus |archive-date=5 October 2025 |ref={{sfnref|Freeman 2020}}}} * {{Cite web |last1=Love |first1=Stephen |date=n.d. |title=Whipple's Penstemon in the Landscape |url=https://cwelwnp.usu.edu/westernnativeplants/plantlist_view.php?id=60&name=penstemonwhippleanus |website=Western Native Plants |publisher=University of Idaho |access-date=25 January 2023}} * {{Cite NatureServe |date=3 October 2025 |id=2.134574 |title=''Penstemon whippleanus'' |access-date=5 October 2025 |ref={{sfnref|NatureServe 2025}}}} * {{Cite usda plants|symbol=PEWHF |title=Penstemon whippleanus |date=5 October 2025 |ref={{sfnref|NRCS 2025}}}} * {{Cite POWO |last1=POWO |date=2025 |id=808349-1 |title=''Penstemon whippleanus'' A.Gray |access-date=5 October 2025 |ref={{sfnref|POWO 2025}}}} * {{Cite web |last1=Schneider |first1=Al |date=2024 |title=''Penstemon whippleanus'' |url=https://www.swcoloradowildflowers.com/Blue%20Purple%20Enlarged%20Photo%20Pages/penstemon%20whippleanus%201.htm |website=Southwest Colorado Wildflowers |url-status=live |archive-url=https://web.archive.org/web/20240613151027/https://www.swcoloradowildflowers.com/Blue%20Purple%20Enlarged%20Photo%20Pages/penstemon%20whippleanus%201.htm |archive-date=13 June 2024 |access-date=5 October 2025}} * {{Cite WFO |last1=WFO |date=2025 |title=''Penstemon arizonicus'' A.Heller |id=0000477044 |access-date=5 October 2025 |ref={{sfnref|WFO 2025a}}}} * {{Cite WFO |last1=WFO |date=2025 |title=''Penstemon glaucus'' var. ''stenosepalus'' A.Gray |id=0001240570 |access-date=5 October 2025 |ref={{sfnref|WFO 2025b}}}} * {{Cite WFO |last1=WFO |date=2025 |title=''Penstemon pallescens'' Osterh. |id= |access-date=5 October 2025 |ref={{sfnref|WFO 2025c}}}} * {{Cite WFO |last1=WFO |date=2025 |title=''Penstemon stenosepalus'' (A.Gray) Howell |id=0001240571 |access-date=5 October 2025 |ref={{sfnref|WFO 2025d}}}} * {{Cite WFO |last1=WFO |date=2025 |title=''Penstemon whippleanus'' A.Gray |id=0001137165 |access-date=5 October 2025 |ref={{sfnref|WFO 2025e}}}} {{Refend}}

==External links== {{Commons}} *[https://www.swcoloradowildflowers.com/Blue%20Purple%20Enlarged%20Photo%20Pages/penstemon%20whippleanus%201.htm Southwest Colorado Wildflowers] *[https://coloradowildflower.com/wildflower/royal-beard-tongue/ Colorado's Wildflowers]

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whippleanus Category:Flora of Arizona Category:Flora of Colorado Category:Flora of Montana Category:Flora of New Mexico Category:Flora of Utah Category:Flora of Wyoming Category:Plants described in 1862