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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

Non-native Species

Global Rank: GNR
State Rank: SNA

Agency Status
USFWS:
USFS:
BLM:
MNPS Threat Rank:
C-value:

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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: 7

(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

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.)

References
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Citation for data on this website:
Big-head Star-thistle — Centaurea macrocephala.  Montana Field Guide.  .  Retrieved on , from