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Montana Field Guide

Montana Field Guides

Scotch Thistle - Onopordum acanthium
Other Names:  Scotch Cotton-thistle, Scotch Cottonthistle

Non-native Species

Global Rank: GNR
State Rank: SNA

Agency Status
MNPS Threat Rank:
C-value: 0

External Links

General Description
Monocarpic biennials or short-lived perennials. Stems erect, branched, 50–200 cm with broad, spiny wings . Herbage glabrate to tomentose, spiny on stems and leaf margins. Leaves clasping, lanceolate, 10–60 cm long, deeply dentate to shallowly pinnately divided into deltoid lobes. Inflorescence 1 to 3 heads at branch tips. Heads discoid; involucres ovoid, 20–35 mm high; phyllaries numerous in 8 to 10 series; the outer spine-tipped, glabrate to tomentose; receptacle flat, fleshy, pitted, naked. Disk flowers perfect, usually purple; corollas slender, 22–25 mm long; style branches fused. Pappus of pinkish, capillary bristles. Achenes obovoid, ribbed, 4–5 mm long, scabrous (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Species Range

Range Comments
Introduced to most of U.S.; native to Eurasia (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Observations in Montana Natural Heritage Program Database
Number of Observations: 247

(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)



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Citation for data on this website:
Scotch Thistle — Onopordum acanthium.  Montana Field Guide.  .  Retrieved on , from