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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
MNPS Threat Rank:

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 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX.)

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

Observations in Montana Natural Heritage Program Database
Number of Observations: 11

(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)


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 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX.)

  • Literature Cited AboveLegend:   View Online Publication
    • 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.
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 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.
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Citation for data on this website:
Big-head Star-thistle — Centaurea macrocephala.  Montana Field Guide.  .  Retrieved on , from