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Montana Field Guide

Montana Field Guides

Squarrose Knapweed - Centaurea virgata
Other Names:  Squarrose Starthistle, Centaurea squarrosa, Centaurea triumfetti

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Non-native Species

Global Rank: GNR
State Rank: SNA
C-value: 1


Agency Status
USFWS:
USFS:
BLM:


 

External Links

 
General Description
Biennial to short-lived perennial. Stems erect, branched, 20–50 cm. Herbage puberulent to sparsely tomentose, glandular-punctate. Leaves petiolate below, the lowest deciduous; blades oblanceolate, 2–10 cm long, deeply pinnate into linear lobes. Inflorescence paniculate with numerous heads; peduncles short. Involucres ovoid, 6–9 mm high; outer phyllaries ovate, striate, tan, spreading spiny-margined; inner linear-lanceolate with scarious lacerate tips. Disk flowers 10 to 14, pink; the outer slender, 3-lobed; corollas 7–9 mm long, as long as the inner. Achenes glabrous, 2–3 mm long; pappus of short bristles, deciduous (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Range Comments
Introduced to OR and MT south to CA, NV, UT. Known from Jefferson and Lewis & Clark counties (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Observations in Montana Natural Heritage Program Database
Number of Observations: 1

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

Recency

 

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



Habitat

Ecology
POLLINATORS
The following animal species have been reported as pollinators of this plant species or its genus where their geographic ranges overlap: Bombus vagans, Bombus bifarius, Bombus centralis, Bombus fervidus, Bombus rufocinctus, Bombus ternarius, Bombus terricola, Bombus occidentalis, Bombus griseocollis, Bombus impatiens, Bombus insularis, and Bombus suckleyi (Thorp et al. 1983, Johnson 1986, Colla and Dumesh 2010, Koch et al. 2012, Williams et al. 2014, Tripoldi and Szalanski 2015).

Management


References
  • Literature Cited AboveLegend:   View Online Publication
    • 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.
    • Flora of North America Editorial Committee. 2006. Flora of North America North of Mexico. Vol. 19. Magnoliophyta: Asteridae, part 6: Asteraceae, part 1. Oxford Univ. Press, New York. xxiv + 579 pp.
    • Johnson, R.A. 1986. Intraspecific resource partitioning in the bumble bees Bombus ternarius and B. pennsylvanicus. Ecology 67:133-138.
    • Koch, J., J. Strange, and P. Williams. 2012. Bumble bees of the western United States. Washington, DC: USDA Forest Service, Pollinator Partnership. 143 p.
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
    • 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: http://dx.doi.org/10.17161/jom.v0i50.4834
    • Williams, P., R. Thorp, L. Richardson, and S. Colla. 2014. Bumble Bees of North America. Princeton, NJ: Princeton University Press. 208 p.
  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2022. Manual of Montana Vascular Plants, Second Edition. Fort Worth, TX: BRIT Press. viii + 779 p.
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Citation for data on this website:
Squarrose Knapweed — Centaurea virgata.  Montana Field Guide.  .  Retrieved on , from