Biennials or monocarpic perennials, 25-100 cm; sometimes perennating by root sprouts. Stems erect, villous with septate trichomes and sometimes thinly arachnoid tomentose; branches 0-few, distal, ascending. Leaves: blades oblong-elliptic, 5-30+ × 2-10 cm, ± undulate, shallowly to deeply pinnatifid, lobes ovate to broadly triangular, usually separated by broad sinuses, spinose-dentate or lobed, main spines 1.5-7 mm, slender to stout, abaxial faces villous with septate trichomes, at least along veins, sometimes thinly arachnoid, adaxial faces villous with septate trichomes and thinly arachnoid tomentose or subglabrous; basal often present at flowering, bases tapered; principal cauline sessile, moderately reduced distally, bases often auriculate-clasping; distal reduced, similar to proximal. Heads 1-few, borne singly at tips of main stem and branches, often closely subtended by 1-several bracts. Peduncles 0-15+ cm (above distal leaves. , leafy-bracted. Involucres broadly cylindric to ovoid, 3.5-5 cm, 2.5-3 cm diam. (appearing much wider and hemispheric to campanulate in pressed specimens), loosely arachnoid on phyllary margins or glabrate. Phyllaries in 8-10 series, imbricate, ovate or lanceolate (outer) to lance-linear (inner), abaxial faces with ± prominent glutinous ridge, outer and middle appressed, apices ascending to spreading, spines 1.5-6 mm; apices of middle and inner narrowed and scabrid-denticulate, innermost spineless, tapered and entire or with expanded, erose-denticulate, flexuous tips. Corollas pink to purple (white), 40-60 mm, tubes 20-35 mm, throats 11-15 mm, lobes 7-10 mm; style tips 3-7 mm. Cypselae stramineous to brown, 3.5-5 mm, apical collars yellow or colored like body; pappi 35-45 mm. 2n = 30.
Flowers of Cirsium pumilum are reportedly sweetly scented.
Stout biennial (sometimes short-lived perennial?) 3-8 dm, with 1-several coarse, slightly thickened roots; herbage green and coarsely arachnoid-villous or crisp-hirsute; lvs lobed or pinnatifid, beset with numerous short marginal spines in addition to the scattered longer ones; basal lvs well developed and generally persistent, these and the lower cauline ones 12-25 נ2-7 cm; cauline lvs not especially crowded except sometimes near the base; heads few or solitary, large, the invol 3.5-5 cm, usually some of its bracts with a narrow, glutinous dorsal ridge; middle and outer invol bracts tipped by a short, ±erect spine; inner bracts elongate, with expanded, chartaceous, crisped and erose tip; fls sweet-scented, purple (white); achenes 3-4 mm; 2n=30. Pastures, old fields, and open woods; s. Me. to w. N.Y., s. to Del., Pa., and in the mts. to Va., e. W.Va., and N.C. (C. odoratum)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.