Search Field Guide
Advanced Search
MT Gov Logo
Montana Field Guide

Montana Field Guides

Big-head Star-thistle - Centaurea macrocephala
Other Names:  Bighead Knapweed, Big Yellow Centaurea, Armenian Basketflower, Yellow Hardhat, Yellow Bachelor's Button, Calypogeia neesiana auct. pro-parte-non (c. Massal. & Carestia) Muell. Frib., Calypogeia muelleriana, Calypogeia neesiana var. meylannii

Non-native Species

Global Rank: GNR
State Rank: SNA

Agency Status


External Links

General Description
Plants: Stems erect, little branched, 50-150 cm; herbage short-villous, thinly arachnoid.

Leaves: Basal and alternate, simple, petiolate below; the blades oblanceolate, 5-30 cm long, entire or dentate, the upper ones wavy-margined, clasping to decurrent.

Inflorescence: Heads discoid, solitary. Involucres hemispheric, about 2-3 cm high; phyllaries well-imbricate in numerous series, the outer ones obovate, green to tan with a brown, scarious, highly fringed appendage wider than the bract; receptacle flat, bristly.

(Adapted from Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX)

Species Range
Montana Range Range Descriptions


Range Comments
Introduced ornamental sparingly escaped in northwest and northeast North America. Known from Gallatin and Pondera Counties in Montana (Adapted from Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX)

Observations in Montana Natural Heritage Program Database
Number of Observations: 19

(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)

Predicted Suitable Habitat Model

This species has a Predicted Suitable Habitat Model available.

To learn how these Models were created see

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).

Reproductive Characteristics
Flowers: Disk flowers perfect, numerous, yellow, the outer ones with a slightly expanded limb, the inner about 2 cm long; style branches short, united with a thickened ring at the base.

Fruit: Achenes ellipsoid, glabrate, 7-8 mm long. Pappus of many flattened bristles.

(Adapted from Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX)


  • 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:
    • 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?
    • Aldrich, D. F. 1978. Overwintering, springtime development and migration of some Aphidea, including Myzus persicae of Northwestern Montana. M.Sc. Thesis. Bozeman, Montana: Montana State University. 112 p.
    • Lesica, P., B. Christiaens, D. Hanna, L. Larsen, and C. Odegard. 2013. Noteworthy collection. MadroƱo 60(3): 262-263.
    • 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.
  • Web Search Engines for Articles on "Big-head Star-thistle"
Login Logout
Citation for data on this website:
Big-head Star-thistle — Centaurea macrocephala.  Montana Field Guide.  .  Retrieved on , from