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Long-styled Thistle - Cirsium longistylum

Species of Concern
Native Species

Global Rank: G2G3
State Rank: S2S3
(see State Rank Reason below)
State Threat Score: Medium
CCVI: Less Vulnerable

Agency Status


External Links

State Rank Reason (see State Rank above)
Population estimates of approximately 30,000 plants, including seven high quality populations, scattered over four mountain ranges are promising for the long-term viability of the species. Habitat in the largest populations is generally of high quality with few if any problem weeds posing significant and immediate threats. In the near future, little change in habitat quality is expected in these populations. Sites are mostly on National Forest lands that provide a degree of protection and two large populations on private lands that have a history of light to moderate grazing appear stable. Also of benefit at this time is the active weed control program employed by the private landowners on their lands.

Long- and short-term population trends are difficult to gauge due to the lack of good survey data over many years. However, available data and observations provide some evidence that population levels have at least remained fairly stable over the past decade, with significant yearly fluctuations possible. Threats posed by invasive weeds and the introduced bio-control agent do provide reason for concern.
  • Details on Status Ranking and Review
    Long-styled Thistle (Cirsium longistylum) Conservation Status Review
    Review Date = 06/06/2012
    View State Conservation Rank Criteria
    Population Size

    Score1 - Moderate: Generally 10,000-100,000 individuals.

    Range Extent

    Score3 - Local Endemic or Very Small Montana Range: Generally restricted to an area <10,000 sq. miles (equivalent to the combined area of Phillips and Valley Counties) or <6 Sub-basins (4th code watersheds) Range-wide OR limited to one Sub-basin in Montana

    Area of Occupancy

    Score0 - High: Occurs in >25 Subwatersheds (6th Code HUC’s).

    Environmental Specificity

    Score1 - Moderate: Species is restricted to a specific habitat that is more widely distributed or to several restricted habitats and is typically dependent upon relatively unaltered, good-quality habitat (C Values of 5-7).


    Score1-2 - Minor to Moderate Declines:


    Score3 - Very High: >70% of the populations are being negatively impacted or are likely to be negatively impacted in the near future by one or more activities or agents that are expected to result in decreased populations and/or decreasing habitat quality and/or quantity.

    CommentIntroduced Rhinocyllus weevil, noxious weeds and weed control efforts are the primary threats.

    Intrinsic Vulnerability

    Score0-1 - Low to Moderate Vulnerability.

    Raw Conservation Status Score

    Score 9 to 11 total points scored out of a possible 19.

General Description
Long-styled Thistle has simple or branched stems that are 50-60 cm tall and up to 15 mm thick at the base; plants are perennial, producing daughter rosettes that live for two more years. The basal leaves are shallowly lobed, moderately spiny, green and glabrous above, and densely white-hairy below; the lower leaves are narrowly lance-shaped, up to 15 cm long, and lobed to 1/3 or less the leaf width. The smaller upper leaves are more ovate in outline with mostly entire margins and numerous marginal spines; the herbage is covered with long, tangled, white hairs. The inflorescence usually consists of a terminal cluster of 2 to several flower heads and a number of side branches which reach up to 15 cm long and have fewer heads; each flower head is ca. 30 mm high, 25 mm wide, and subtended by a few reduced leaves. The involucral bracts occur in two main series: the outer are narrowly lance-shaped with a yellowish, dilated, and fringed apex tipped by a slender spine; the inner bracts are more lance-shaped and longer. The white disk flowers are 20-22 mm long; ray flowers are absent. There are numerous tawny bristles which form a pappus at the tip of the achene.

Flowering in late June-August.

Diagnostic Characteristics
On first-glance thistles can look similar, but upon closer inspection differences become apparent.
Thistles belong to the genera of Cirsium, Carduus, and Onopordum. They are separated by:

* Feathery (plumose) pappus, which have fine, long hairs on each side of the main bristle.
* Receptacle of flower head has bristles. Look between florets within a flower head to find them.

* Capillary pappus, which are minutely barbed, narrow bristles.
* Receptacle of flower head has bristles. Look between florets within a flower head to find them.

* Receptacle of flower head has no bristles. Look between florets within a flower head to find nothing.
* Entire lengths of stems have spiny wings.
* Foliage is silvery gray.

Native versus Exotic (Source: Parkinson and Mangold 2015)
* Native thistles tend to have involucral bracts adhere to the flower head for most of their length (except for the spine).
* Native thistles tend to grow scattered across a habitat, spreading slowly with disturbance, and contribute to plant diversity.
* Exotic thistles grow quickly with disturbance, forming dense patches that interfere with access, and through competition often reduces plant diversity.

Montana has 12 species of Cirsium, and only 6 are described below.

Long-styled Thistle - Cirsium longistylum, native, Montana endemic, and SOC
* Upper leaf surface lacks spines.
* Inner & outer bracts are wide, scarious, and with erose tips AND outer bracts have a raised, darkened, and resinous keel.
* Flower heads have involucres more than 2 cm tall [examine larger heads].
* Resembles Hooker Thistle the most.

Hooker Thistle - Cirsium hookerianum, native and desirable
* Heads mostly clustered.
* Flower head stems (peduncles) are more than 2cm long.
* Flower heads have involucres of 2-3 cm tall [examine larger heads].
* Involucral bracts not erose, dilated, and scarious, but do have cobwebby hairs.
* Upper leaves mostly do NOT enclose the flower heads.
* Leaves are densely tomentose beneath and succulent.

Wavyleaf Thistle - Cirsium undulatum, native and desirable
* Upper leaf surface lacks spines AND white-tomentose hairs making it appear gray.
* Involucral bracts tend to point upwards with inner bracts acuminate.
* Flower heads have involucres more than 2 cm tall [examine larger heads].
* Most flower heads not clustered and peduncles more than 2 cm long.

Flodman’s Thistle - Cirsium flodmanii, native and desirable
* Upper leaf surface lacks spines AND has sparse white-tomentose hairs making it appear green.
* Involucral bracts tend to point upwards with inner bracts acuminate.
* Flower heads have involucres more than 2 cm tall [examine larger heads].
* Most flower heads are not clustered and some peduncles are more than 2 cm long.

Canada Thistle - Cirsium arvense, exotic and Noxious
* Flower heads have involucres less than 2 cm tall [examine larger heads].
* Each flower head consists of either male florets or female florets.
* Leaves are arachnoid-villous, but the green leaf remains visible.
* Stems lack an obvious winged stem.
* Plants are strongly rhizomatous.

Bull ThistleCirsium vulgare, exotic and undesirable
* Flower heads are mostly single at stem tips and arranged in an open inflorescence.
* Flower heads have involucres more than 2 cm tall [examine larger heads].
* On the flower head the outer bracts tend to point outwards and upwards, are needle-like and long.
* Leaves are deeply lobed, green beneath with cobwebby hairs and obvious white veins.
* Leaves have many sharp, short spines. Entire plant has spines, some very long, making it difficult to touch without injury.
* Plants are taprooted.

Scotch ThistleOnopordum acanthium, exotic and undesirable
* Receptacle of flower head has no bristles.
* Entire lengths of stems have spiny wings, becoming broad and spiny.
* Foliage is silvery gray and can grow taller than 6 feet.

Musk Thistle - Carduus nutans, exotic and undesirable
* Flower heads have involucral bracts that are broadly triangular, have smooth margins, and a short spine-tip.
* Heads nod as flowers mature.

Species Range
Montana Range Range Descriptions


Range Comments
Endemic to central Montana with extant populations in Broadwater, Cascade, Judith Basin, Lewis & Clark, Meagher and Wheatland counties.

Observations in Montana Natural Heritage Program Database
Number of Observations: 274

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)

C. longistylum occurs in a variety of open habitats that receive full to partial sun. The best habitats for the species occur in montane to subalpine meadows. Occurrences are also common along roadsides, herbaceous-dominated riparian areas and open forests of Douglas-fir, lodgepole pine or whitebark pine. Plants occur as low 4800 feet elevation up to approximately 8100 feet with the majority of the occurrences between approximately 6000 and 7500 feet. Known occurrences of C longistylum are predominantly on calcareous soils derived from dolomites, limestones or shales.
Predicted Suitable Habitat Model

This species has a Predicted Suitable Habitat Model available.

To learn how these Models were created see

Ecological Systems Associated with this Species

The following animal species have been reported as pollinators of this plant species or its genus where their geographic ranges overlap: Bombus vagans, Bombus appositus, Bombus auricomus, Bombus bifarius, Bombus borealis, Bombus centralis, Bombus fervidus, Bombus flavifrons, Bombus frigidus, Bombus huntii, Bombus mixtus, Bombus nevadensis, Bombus rufocinctus, Bombus sylvicola, Bombus ternarius, Bombus terricola, Bombus sitkensis, Bombus occidentalis, Bombus pensylvanicus, Bombus bimaculatus, Bombus griseocollis, Bombus impatiens, Bombus insularis, Bombus suckleyi, Bombus bohemicus, and Bombus flavidus (Thorp et al. 1983, Mayer et al. 2000, Wilson et al. 2010, Colla and Dumesh 2010, Colla et al. 2011, Koch et al. 2012, Williams et al. 2014, Tripoldi and Szalanski 2015).

Threats or Limiting Factors
Reported threats to Montana's populations of Long-styled Thistle include populations occurring with non-native species, and chemical and biological controls applied to manage them (MTNHP Threat Assessment 2021). Competition from the spread of non-native plants Canada Thistle (Cirsium arvense), Common Hound’s-tongue (Cynoglossum officinale), and Spotted Knapweed (Centaurea stoebe). Especially where Long-styled Thistle occurs alongside other non-native thistle species, it is occasionally sprayed with chemical herbicide. Concern that some biological controls intended to target Canada Thistle will impact native thistle populations is credible. Existing impacts are not well understood, and further study of the relationship between Long-styled Thistle and biological controls are needed.

  • Literature Cited AboveLegend:   View Online Publication
    • Colla, S., L. Richardson, and P. Williams. 2011. Bumble bees of the eastern United States. Washington, DC: USDA Forest Service, Pollinator Partnership. 103 p.
    • Colla, S.R. and S. Dumesh. 2010. The bumble bees of southern Ontario: notes on natural history and distribution. Journal of the Entomological Society of Ontario 141:39-68.
    • Koch, J., J. Strange, and P. Williams. 2012. Bumble bees of the western United States. Washington, DC: USDA Forest Service, Pollinator Partnership. 143 p.
    • Mayer, D.F., E.R. Miliczky, B.F. Finnigan, and C.A. Johnson. 2000. The bee fauna (Hymenoptera: Apoidea) of southeastern Washington. Journal of the Entomological Society of British Columbia 97: 25-31.
    • Parkinson, Hilary and Jane Mangold. 2015. Guide to Exotic Thistles of Montana and How to Differentiate from Native Thistles. EB0221. Montana State University Extension, Bozeman, Montana.
    • Thorp, R.W., D.S. Horning, and L.L. Dunning. 1983. Bumble bees and cuckoo bumble bees of California (Hymenoptera: Apidae). Bulletin of the California Insect Survey 23:1-79.
    • Tripoldi, A.D. and A.L. Szalanski. 2015. The bumble bees (Hymenoptera: Apidae: Bombus) of Arkansas, fifty years later. Journal of Melittology 50: doi:
    • Williams, P., R. Thorp, L. Richardson, and S. Colla. 2014. Bumble Bees of North America. Princeton, NJ: Princeton University Press. 208 p.
    • Wilson, J.S., L.E. Wilson, L.D. Loftis, and T. Griswold. 2010. The montane bee fauna of north central Washington, USA, with floral associations. Western North American Naturalist 70(2): 198-207.
  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Achuff, P. L. and L. A. Schassberger Roe. 1991. Weeds and rare native plants in Montana. Proc. Weed Symposium (1991): 18-23.
    • Biosystems Analysis, Inc. 1994. Endangered species biological survey final report. [Contract F24604 93 C0324]. Submitted to D. Spitzer, Malmstrom Air Force Base. 47 pp. plus appendices.
    • Brunsfeld, S.J. and C.T. Baldwin. 1994. Preliminary genetic analysis of Cirsium longistylum (Long-styled thistle), a candidate threatened species. Unpublished report prepared for the U.S. Fish and Wildlife Service, Region 4. Wildland Plant Ecogenetics Cooperative, in cooperation with the Montana Natural Heritage Program, Helena. 20 pp. plus appendices.
    • Heidel, B.L. 1994. Monitoring study of Cirsium longistylum (long-styled thistle), a candidate threatened species. Unpublished report prepared for U.S. Fish and Wildlife Service, Region 4. Montana Natural Heritage Program, Helena, MT. 32 pp.
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
    • Mathews, S.Y. 1990. Cirsium longistylum project: summary report. Unpublished report. Montana Natural Heritage Program, Helena, MT. 3 pp.
    • Mincemoyer, S. 2004. Range-wide status assessment of Cirsium longistylum (long-styled thistle). Report to Burnett Land, LLC. Montana Natural Heritage Program, Helena, MT. 22 pp. + appendices.
    • Moore, R.J. and C. Frankton. 1963. Cytotaxonomic notes on some Cirsium species of the western United States. Canadian Journal of Botany 41:1553-1567.
    • Poole, J.M. and B.L. Heidel. 1993. A taxonomic assessment and monitoring study of the Long-styled Thistle (Cirsium longistylum). Unpublished report to the U.S. Fish and Wildlife Service. Montana Natural Heritage Program, Helena, MT. 97 pp.
    • Poole, J.M. and B.L. Heidel. 1993. Sensitive plant surveys in the Big Belt and Elkhorn Mountains, Helena National Forest, Montana. Unpublished report to the Helena National Forest. Montana Natural Heritage Program. Helena, MT. 129 pp. plus printouts, maps.
    • Schassberger, L.A. 1991. Report on the conservation status of Cirsium longistylum, a candidate threatened species. Unpublished report. Montana Natural Heritage Program, Helena, MT 92 pp.
    • Schassberger, L.A. and P.L. Achuff. 1991. Status review of Cirsium longistylum, Lewis & Clark National Forest. Montana Natural Heritage Program. Helena, MT 78 pp.
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Citation for data on this website:
Long-styled Thistle — Cirsium longistylum.  Montana Field Guide.  .  Retrieved on , from