This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol3", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Biennial; stem stout, branched, more or less tomentose, 3°-5° high, leafy to the heads. Leaves dark green, lanceolate, acuminate, deeply pinnatifid. 3'-6' long, or the lowest larger, decurrent on the stem and branches, the lobes triangular-lanceolate, tipped with stout prickles, the margins and decurrent bases bristly, the upper surface strigose-pubescent or hispid, the lower brown-tomentose and midnerve pilose, especially when young; heads mostly solitary at the ends of the branches, 1 1/2'-2' broad, 1 1/2'-2' high; bracts of the involucre cottony, narrowly lanceolate, acuminate, all tipped with slender, erect or ascending prickles; flowers dark purple.
In fields and waste places, Newfoundland to Georgia, Minnesota, Nebraska, Oregon and California. Naturalized from Europe. Native also of Asia. Plume-, bank-or horse-thistle, bell-, bird-, blue-, button-, boar-, bull- or roadside-thistle. July-Nov.
Carduuse altissimus L. Sp. Pl. 824. 1753. Cnicus altissimus Willd. Sp. Pl. 3: 1671. 1804. Cirsium altissimum Spreng. Syst. 3: 373. 1826.
Biennial or perennial; roots often thickened; stem pubescent or tomentose, stout, branched, leafy to the heads, 3°-10° high. Leaves ovate-oblong or oblong-lanceolate, sessile or slightly clasping, sparingly pubescent above, densely white-tomentose beneath, scarcely or not at all decurrent, acute, spinu-lose-margined, entire, dentate with bristle-pointed teeth or lobed, sometimes pinnatifid into oblong or triangular-lanceolate segments, the lowest sometimes 8' long, narrowed into margined petioles, the uppermost linear or lanceolate, much smaller; heads about 2' broad, 1 1/2'-2' high, mostly solitary at the ends of the branches; outer bracts of the involucre ovate or ovate-lanceolate, firm with a dark, slightly glandular spot or band on the beak, tipped with short prickles, the inner linear-lanceolate, acuminate, unarmed; flowers light purple.
In fields and thickets, Massachusetts to Ohio, Minnesota, Florida, Nebraska and Texas. Aug.-Sept.
Cirsium iowense Pammel, with slightly larger heads and longer-tipped inner involucral bracts, appears to be a northwestern race of this species.
Similar to the preceding species, but lower and more leafy, seldom over 7° high. Leaves deeply pinnatifid into linear, linear-lanceolate or falcate, prickly toothed segments, white tomentose beneath, sessile, the basal ones sometimes 12' long; heads 1 1/2'-2' broad, about 1 1/2' high, usually involucrate by the upper leaves, mostly solitary at the ends of the branches; outer bracts of the involucre coriaceous, ovate, slightly woolly, tipped with slender bristles, which are longer than those of the preceding species; inner bracts lanceolate, acuminate, unarmed; flowers light purple or pink, rarely white.
In fields and along roadsides, New Brunswick to Ontario, Georgia, Minnesota, Nebraska and Missouri. July-Nov.