Carduus pycnocephalus
Italian plumeless thistle

Distribution: Occurring west of the Cascades crest in Washington, where known only from Clallam County; Washington to California and Idaho, also in central and eastern U.S.

Habitat: Disturbed, open areas at low elevation.

Flowers: June-July

Origin: Introduced from Europe

Growth Duration: Annual

Conservation Status: Not of concern


Annuals, 20-200 cm in total height, stems simple to openly branched, loosely tomentose with fine single-celled hairs and sessile growths with curled, septate hairs; teeth of wings up to 10 mm, wing spines to 20 mm.


Basal leaves tapering to winged petioles, blades 10–25 cm, margins pinnately 2 to 5 lobed, abaxial faces ± tomentose, adaxial faces tomentose and pilose, often glabrate; cauline leaves sessile, shorter, margins less divided than basal, distally reduced to bracts.


Heads borne singly or clustered in tight groups of 2-5, heads at ends of branches and sometimes in upper axils, sessile or short-pedunculate, 20–25 mm; peduncles winged throughout or unwinged, 0–2 cm long, tomentose; involucres cylindric to ellipsoid, 17–22 mm diameter; phyllaries linear to lanceolate, with appressed loosely tomentose bases, 2–3 mm wide and ascending, linear appendages 0.5–1.5 mm wide, not scarious, distally scabrous on midribs and margins, spine tips 1–3 mm, inner straight and erect, with unarmed or minutely armed tips; Corollas purple, dark purple, or pink, 14–16 mm long tube; lobes 3 times longer than throat.


Cypselae ellipsoid, golden to brown, 4–6 mm, finely 20-nerved; pappus bristles 15–20 mm.

Accepted Name:
Carduus pycnocephalus L.
Publication: Sp. Pl. Ed. 2,. 2: 1151. 1763.

Synonyms & Misapplications:
(none provided)
Additional Resources:

PNW Herbaria: Specimen records of Carduus pycnocephalus in the Consortium of Pacific Northwest Herbaria database.

WA Flora Checklist: Carduus pycnocephalus checklist entry.

OregonFlora: Carduus pycnocephalus information.

E-Flora BC: Carduus pycnocephalus atlas page.

CalPhotos: Carduus pycnocephalus photos.

USDA Plants: Carduus pycnocephalus information.

10 photographs:
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