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Cirsium harrisonii

(S.L. Welsh) Ackerfield & D.J. Keil

Harrison's Thistle

G1Critically Imperiled Found in 2 roadless areas NatureServe Explorer →
G1Critically ImperiledGlobal Rank
UnknownThreat Impact
Identity
Unique IDELEMENT_GLOBAL.2.130138
Element CodePDAST2E102
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryVascular Plant
Endemicendemic to a single state or province
KingdomPlantae
PhylumAnthophyta
ClassDicotyledoneae
OrderAsterales
FamilyAsteraceae
GenusCirsium
Synonyms
Cirsium eatonii var. harrisoniiWelsh
Concept Reference
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.
Taxonomic Comments
Cirsium harrisonii was included by Kartesz (1999) in C. eatonii without recognition of varieties. In FNA (vol. 19, 2006), seven varieties are recognized and var. harrisonii is lumped with the typical variety. Ackerfield et al. (2020) and Siniscalchi et al. (2023) elevate this entity to the species level.
Conservation Status
Rank Method Rank calculation - Biotics v2
Review Date2025-04-08
Change Date1995-04-19
Edition Date2025-04-08
Edition AuthorsM. McCormick (2021) and N. Ventrella (2025)
Threat ImpactUnknown
Range Extent<100 square km (less than about 40 square miles)
Number of Occurrences1 - 20
Rank Reasons
Cirsium harrisonii is a perennial forb occurring in alpine communities on talus scree slopes and in meadows of the Tushar Mountains of Beaver and Piute counties, Utah. There are an estimated three to six occurrences of this species located primarily on U.S. Forest Service-administered land in Fishlake National Forest. Threats to Cirsium harrisonii include grazing-related impacts, particularly from non-native introduced mountain goats, and climate change and drought. Past taxonomic confusion has limited data collection for this species, and little is known about its distribution, population size, threats, and trends.
Range Extent Comments
Cirsium harrisonii is endemic to the western United States, where it is restricted to the Tushar Mountains of Beaver and Piute counties, Utah (Welsh et al. 2015). Range extent was estimated using data from the Utah Rare Plant Database (2021), herbarium specimens, photo-based observations, and NatureServe Network occurrence data collected between 1984 and 2025 (GBIF 2025, iNaturalist 2025, NatureServe 2025, RARECAT 2025, SEINet 2025).
Occurrences Comments
By applying a 1 km separation distance to data from the Utah Rare Plant Database (2021), herbarium specimens, photo-based observations, and NatureServe Network occurrence data documented between 1984 and 2025, it is estimated that there are six occurrences rangewide (GBIF 2025, iNaturalist 2025, NatureServe 2025, RARECAT 2025, SEINet 2025). There are three estimated occurrences using a 2km separation distance, which is the distance used by the Utah Natural Heritage Program to delineate populations (2021).
Threat Impact Comments
Threats to Cirsium harrisonii include grazing-related impacts, and climate change and drought (UNHP 2021, UNPS 2025). Mountain goats were introduced to the Tushar Mountains in 1986 for the purpose of big game hunting, and are now naturalized to the region (Taye 1995). This species is threatened, at least at the type locality in the Tushar Mountains, by grazing-related impacts from cattle and naturalized mountain goats, though the magnitude of this impact has not been assessed (UNHP 2021). Climate change is also a threat likely impacting this species throughout it's range (Wrobleski 2023). Droughts and rapid snowmelt due to wind-blown sediments are melting snowpack earlier than usual in the region (UNPS 2025). According to the Utah Native Plant Society (2025), "threats are high in at least the Tushar Mountains, but it is not known if that holds true throughout this taxon's potential range in Utah".
Ecology & Habitat

Habitat

Cirsium harrisonii is associated with alpine communities on talus slopes and meadows from 2975 to 3450 m in elevation (Welsh et al. 2015). This species is most often found in subalpine communities on talus scree and slopes (Taye 1995).
Terrestrial Habitats
AlpineBare rock/talus/scree
Other Nations (1)
United StatesN1
ProvinceRankNative
UtahS1Yes
Threat Assessments
ThreatScopeSeverityTiming
2 - Agriculture & aquaculturePervasive (71-100%)UnknownHigh (continuing)
2.3 - Livestock farming & ranchingPervasive (71-100%)UnknownHigh (continuing)
8 - Invasive & other problematic species, genes & diseasesPervasive (71-100%)UnknownHigh (continuing)
8.4 - Problematic species/diseases of unknown originPervasive (71-100%)UnknownHigh (continuing)
8.4.2 - Named speciesPervasive (71-100%)UnknownHigh (continuing)
11 - Climate change & severe weatherPervasive (71-100%)UnknownHigh (continuing)
11.1 - Habitat shifting & alterationPervasive (71-100%)UnknownHigh (continuing)
11.2 - DroughtsPervasive (71-100%)UnknownHigh (continuing)

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Plant Characteristics
DurationPERENNIAL, Long-lived
Economic Value (Genus)No
Roadless Areas (2)
Utah (2)
AreaForestAcres
Bullion - DelanoFishlake National Forest14,917
Tushar MountainFishlake National Forest39,992
References (19)
  1. Ackerfield, J.R., D.J. Keil, W.C. Hodgson, M.P. Simmons, S.D. Fehlberg, and V.A. Funk. 2020. Thistle be a mess: Untangling the taxonomy of <i>Cirsium </i>(Cardueae: Compositae) in North America. Journal of Systematics and Evolution 58(6): 881-912.
  2. Cronquist, A. 1994. Asterales. In A. Cronquist, A.H. Holmgren, N.H. Holmgren, J.L. Reveal, and P.K. Holmgren. Intermountain flora: Vascular plants of the Intermountain West, U.S.A. Vol. 5. New York Botanical Garden, Bronx. 496 pp.
  3. Flora of North America Editorial Committee, editor. 2006a. Flora of North America, north of Mexico. Volume 19. Magnoliophyta: Asteridae, part 6: Asteraceae, part 1. Oxford University Press, New York. 579 pp.
  4. Global Biodiversity Information Facility (GBIF). 2025. Global Biodiversity Information Facility (GBIF) data portal. Online. Available: https://www.gbif.org/ (accessed 2025).
  5. iNaturalist. 2025. Online. Available: https://www.inaturalist.org (accessed 2025).
  6. 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.
  7. NatureServe. 2025. NatureServe Network Biodiversity Location Data. NatureServe, Arlington, Virginia.
  8. NatureServe. Unpublished. Concept reference for taxa for which no reference which describes the circumscription has been recorded; to be used as a placeholder until such a citation is identified.
  9. <p>NatureServe's Rapid Analysis of Rarity and Endangerment Conservation Assessment Tool (RARECAT). 2025. Version: 2.1.1 (released April 04, 2025).</p>
  10. Siniscalchi, C.M., J.R. Ackerfield, and R.A. Folk. 2023. Diversification and biogeography of North American thistles (<i>Cirsium</i>: Carduoideae: Compositae): Drivers of a rapid continent-wide radiation. International Journal of Plant Sciences 184: 322-341.
  11. Southwest Environmental Information Network (SEINet). 2025. Collections Databases. Online. Available: https://swbiodiversity.org/seinet/collections/index.php (accessed 2025).
  12. Taye, A. C. 1995. Alpine vascular flora of the Tushar Mountains, Utah. Great Basin Naturalist 55(3): 225-236.
  13. U.S. Geological Survey (USGS). 2024. Gap Analysis Project (GAP) Protected Areas Database of the United States (PAD-US) 4.0: U.S. Geological Survey data release. Online. Available: https://doi.org/10.5066/P96WBCHS (accessed 2025).
  14. Utah Native Plant Society (UNPS). 2003-2021. Utah rare plant guide. A.J. Frates editor/coordinator. Salt Lake City, UT. Utah Native Plant Society. Online. Available: https://www.utahrareplants.org (accessed 2021).
  15. Utah Native Plant Society (UNPS). 2025. 2016-2025 UNPS Utah Rare Plant Master List . Online. Available: www.utahrareplants.org/rpg_species.html (Accessed 2025).
  16. Utah Natural Heritage Program. 2021. Utah Rare Plant Database. (Accessed 2021).
  17. Utah Natural Heritage Program (UNHP). 2021. Element Subnational Ranking Form: <i>Cirsium harrisonii</i> in Biotics 5 database. NatureServe, Arlington, Virginia (accessed 8 April 2025).
  18. Welsh, S.L., N.D. Atwood, S. Goodrich, and L.C. Higgins. (Eds). 2015. A Utah flora, fifth edition, revised 2015. Monte L. Bean Life Science Museum, Provo, Utah. 987 pp.
  19. Wrobleski, A., Ernst, S., Weber, T., and A. Delach. 2023. The impact of climate change on endangered plants and lichen. PLOS Climate 2(7): e0000225.