Herbs 0.5-1.5 m tall, perennial. Stem solitary, branched, with dense long multicellular hairs and sparsely cobwebby. Leaves papery, abaxially grayish white, sparsely cobwebby to lanate, and with long multicellular hairs, adaxially green and densely strigose. Basal and lower cauline leaves petiolate; leaf blade broadly lanceolate, 15-24 × 5-10 cm, pinnatifid; segments 3-5 pairs, triangular to lanceolate, with spiny teeth and acuminate spiny apex. Upper cauline leaves sessile, gradually smaller upward. Pseudocephalia 1-3, 4-4.5 cm in diam. Phyllaries 14-18; outermost phyllaries narrowly oblanceolate, ca. 1 cm, ca. 1/2 as long as involucre, claw margin long ciliate, distal portion brown, broadly elliptic, abaxially densely strigose and gland-dotted, margin long ciliate, and apex spinulose acuminate; middle phyllaries oblanceolate to narrowly elliptic, ca. 1.2 cm, abaxially densely strigose, margin long ciliate; inner phyllaries lanceolate, abaxially densely strigose, apex dentate. Corolla blue to white, tube outside not gland-dotted or sparsely gland-dotted. Achene ca. 7 mm, hairs yellowish. Pappus scales ca. 1.2 mm, connate almost entirely. Fl. and fr. Aug-Sep. 2n = 30, 32.
Plants 100–200 cm. Stems simple to much branched, ± glandular, ± tomentose. Leaves: basal and proximal cauline leaves shortly winged-petiolate, distal cauline sessile, clasping; blades oblong-elliptic to narrowly obovate, margins ± subentire or 1–2-pinnately lobed, lobes lanceolate to triangular, margins revolute, spiny-dentate, spine-tipped, spines slender, 2–4 mm; abaxial faces densely gray- or white-tomentose, adaxial faces green, glandular-scabrous. Secondary heads 3–6 cm diam. Involucres 15–25 mm. Outer phyllaries ± glandular, inner phyllary apices attenuate, expanded, fringed. Corollas white to pale blue, 12–14 mm, tube ca. 5.5 mm, lobes ca. 7 mm. Cypselae 7–10 mm; pappi of ± connate, ciliate scales 1–1.5 mm. 2n = 30, 32.
"Coarse, branching, to 2.5 m; stem spreading-hairy (some of the hairs gland-tipped), also tomentose above; lvs white-tomentose beneath, green and merely scabrous or hirsute above (many of the hairs gland-tipped), sessile and clasping (at least the middle and upper), not decurrent, pinnatifid, to 3.5 × 2 dm; secondary heads naked-pedunculate, 3.5–6 cm thick, pale bluish; proper invol 1.5–2 cm, its bracts puberulent on the back; subtending bristles seldom half as long as the invol; 2n=30, 32. Waste places; native of Eurasia, sometimes cult., and casually established as a weed here and there in e. U.S. and adj. Can. July–Sept."