Flora of North America species comparison

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Onopordum acanthium

Onopordum acanthium subsp. acanthium

cotton thistle, onoporde acanthe, Scotch cotton-thistle, Scotch-thistle, Scots thistle
Photo is of parent taxon

cotton thistle, Scotch cottonthistle, Scotch-thistle, Scots thistle, Scottish thistle
Habit Plants 50–400 cm, herbage canescent-tomentose throughout or ± glabrescent.
Stems

appressed-hairy;

wings to 15 mm wide.
Leaves

10–60 cm, margins dentate to shallowly pinnatifid, lobes 8–10 pairs, broadly triangular, densely tomentose, especially on abaxial faces.
Involucres

± spheric, 20 mm diam. (excluding spines), bases truncate to concave.
Corollas

purple or white, 22–25 mm, lobes glabrous.
Phyllaries

linear, bases 2–2.5 mm wide, puberulent, ± cobwebby-tomentose, spines to 6 mm, adaxially glabrous.
Heads

mostly in clusters of 2–3, at tips of branches.
Cypselae

4–5 mm, transversely roughened;

pappi of many pink to reddish, minutely barbed bristles 7–9 mm.
2n

= 34.

Onopordum acanthium

Onopordum acanthium subsp. acanthium
Phenology Flowering summer (Jun–Sep).
Habitat Grasslands, woodlands, riparian areas, deserts, disturbed ground, roadsides
Elevation 0–2200 m (0–7200 ft)
Distribution
from FNA
AL; AZ; CA; CO; CT; DE; FL; IA; ID; IL; IN; KS; KY; MA; MD; MI; MN; MO; MT; NE; NJ; NM; NV; NY; OH; OK; OR; PA; RI; TX; UT; VA; VT; WA; WI; WV; WY; BC; NB; NS; ON; QC; Eurasia
[WildflowerSearch map]
[BONAP county map]
from FNA
AL; AZ; CA; CO; CT; DE; FL; IA; ID; IL; IN; KS; KY; MA; MD; MI; MN; MO; MT; NE; NJ; NM; NV; NY; OH; OK; OR; PA; RI; TX; UT; VA; VT; WA; WI; WV; WY; BC; NB; NS; ON; QC [Introduced in North America; Eurasia, introduced in Australia]
Discussion

Subspecies 3 (1 in the flora).

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Scotch thistle is the national emblem of Scotland. Although it is sometimes cultivated as an ornamental, Scotch thistle is considered to be a noxious weed both in Canada and the United States. Infestations severely degrade rangelands, and dense stands are practically impenetrable because of the spiny nature and large size of the plant. This species has also invaded rangelands in Australia.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 19, p. 88. FNA vol. 19, p. 88.
Parent taxa Asteraceae > tribe Cardueae > Onopordum Asteraceae > tribe Cardueae > Onopordum > Onopordum acanthium
Sibling taxa
O. illyricum, O. tauricum
Subordinate taxa
O. acanthium subsp. acanthium
Name authority Linnaeus: Sp. Pl. 2: 827. (1753) unknown
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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