Penstemon laricifolius ssp. exilifolius
Author: (A. Nels.) Keck


Larch-leaf beardtongue


Scrophulariaceae (Figwort Family)

Close up of Penstemon laricifolius ssp. exilifolius by Carol English.
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Close up of Penstemon laricifolius ssp. exilifolius by Ann M. Grant.
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Close up of Penstemon laricifolius ssp. exilifolius by Ann M. Grant.
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Taxonomic Comments

Ackerfield (2015) and others place the genus Penstemon in the Plantaginaceae or the Plantain Family.

Ranks and Status

Global rank: G4T3
State rank: S2
Federal protection status: None
State protection status: None

[+] Description and Phenology

Penstemon laricifolius ssp. exilifolius by Bonnie Heidel.
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General description: Penstemon laricifolius ssp. exilifolius is a perennial with several to numerous stems arising 10 to 20 (34) cm from a branched caudex. Leaves are numerous, narrowly linear to filiform, 15 to 25 mm long, and in dense, erect clusters on the caudex. Flowers are borne in a narrow inflorescence, few- to many-flowered; pedicels slender, sepals lanceolate and long-acuminate, with scarious margins. Corolla is white, greenish white, or light rose outside, somewhat abruptly inflated, 12 to 15 mm long, with glabrous anthers that dehisce their full length and at the suture; the sterile filament is very stiffly and densely short-pubescent. Inflorescence is a raceme with 1 (few) flowers per node and nodes that are slightly overlapping to remote (Heidel and Handley 2007, Ackerfield 2017).

Look Alikes: The filiform leaves and small white flowers are distinctive.

Phenology: Flowers late June through August. Fruiting in August (Colorado Natural Heritage Program occurrence records).

[+] Herbarium Photos

Images of Penstemon laricifolius ssp. exilifolius housed at the Colorado State University Herbarium.

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[+] Habitat

Habitat of Penstemon laricifolius ssp. exilifolius by Ann M. Grant.
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Habitat of Penstemon laricifolius ssp. exilifolius by Jessica Smith.
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In Colorado, this subspecies is found in grasslands and sagebrush meadows (Ackerfield 2015). Associated taxa include: Artemisia spp., Festuca idahoensis, Artemisia frigida, Chrysothamnus viscidiflorus, Muhlenbergia montana, Bouteloua gracilis, Eriogonum umbellatum, Lupinus argenteus, Oxytropis sericea, and Sedum lanceolatum. 

Elevation Range: 7,592 - 9,406 feet (2,314 - 2,867 meters)

[+] Distribution

Distribution of Penstemon laricifolius ssp. exilifolius in Colorado according to mapped land ownership/management boundaries (CNHP 2017, COMaP).
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Distribution of Penstemon laricifolius ssp. exilifolius in Colorado.
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Colorado endemic: No
Global range: Global range is limited to one county in Colorado, and six counties in Wyoming (USDA NRCS 2017).
State range: Known from the Laramie River Valley in Larimer County, Colorado. Also known from Wyoming.

[+] Threats and Management Issues

In Colorado, one occurrence reports a nearby housing development as a potential threat. Another reports recreational use as a potential threat, and one reports road, powerline work, and weeds as potential threats. Colorado climate scenarios for 2050 suggest temperature will increase by 3-7 F and precipitation may decrease or increase. The impact to any given rare plant habitat is likely to vary. Long-term monitoring that includes weather and soil moisture data is critical to understanding climate impacts.

[+] References

    • Beardsley, M. and D. A. Steingraeber. 2013. Population dynamics, rarity and risk of extirpation for populations of Mimulus gemmiparus (budding monkeyflower) on National Forests of Colorado. A research report submitted to the USFS Forest Service. Arapaho and Roosevelt National Forets and Pawnee National Grassland. pp 17. Accessed online on May 11 at: http://www.r5.fs.fed.us/wildflowers/Rare_Plants/profiles/Critically_Imperiled/mimulus_gemmiparus/ documents/USFS_MimulusStatusReport2013.pdf
    • Colorado Natural Heritage Program and the Geospatial Centroid. 2017. The Colorado Ownership and Protection Map (COMaP). Colorado State University, Ft. Collins, CO.
    • Dorn, R. D. 2001. Vascular Plants of Wyoming. 3rd edition. Mountain West Publishing. Cheyenne, Wyoming. 412 pp.
    • Harrington, H. D. 1954. Manual of the Plants of Colorado. Sage Books, Denver, CO. 666 pp.
    • Heidel, B. and J. Handley. 2007. Penstemon laricifolius Hook. & Arn. ssp. exilifolius (A. Nels.) D.D. Keck (larchleaf beardtongue): a technical conservation assessment. [Online]. USDA Forest Service, Rocky Mountain Region. Available: http://www.fs.fed.us/r2/projects/scp/assessments/penstemonlaricifoliussspexilifolius.pdf.
    • Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
    • Keck. 1937. Studies in Penstemon. Bulletin of the Torrey Club. Vol. 64.
    • Payson, E.B. 1924. The Species of Penstemon native of Wyoming. Univ. of Wyoming Publ. Science 4:88-103.
    • USDA, Natural Resources Conservation Service, PLANTS Database [USDA PLANTS]. http://plants.usda.gov/. Accessed 2017.
    • Weber, W. A. and R. C. Wittmann. 2012. Colorado Flora, Eastern Slope, A Field Guide to the Vascular Plants, Fourth Edition. Boulder, Colorado. 555 pp.

Last Updated

2017-02-09