This section is from the book "A Manual Of Weeds", by Ada E. Georgia. Also available from Amazon: A Manual Of Weeds.
Introduced. Annual. Propagates by seeds.
Time of bloom: June to September.
Seed-time: August to November.
Range: Atlantic States from Massachusetts to North Carolina; also on the Pacific Coast. Habitat: Pastures, roadsides, waste places.
A bushy, deep green, leafy plant, one to two feet tall. Leaves only slightly hairy, the lower ones pinnately divided into lance-shaped, irregularly toothed lobes, the petioles often narrowly winged but not decurrent; the upper ones undivided, sessile, slightly clasping, the teeth on all slightly spinulose but not prickly. Heads about an inch broad, sessile or on very short peduncles, terminal, or in the forks, or scattered along the branches; involucre ovoid, and all but its innermost row of bracts tipped with stout, sharp, light yellow, spreading spines, a half-inch to an inch long, each fierce pricker subtended by one to four pairs of harmless little spines at its broadened base. Florets all tubular, the corollas reddish purple, the outer row sterile, the rest perfect and fertile. Achenes brown, flattened, obscurely four-sided, smooth, and without a pappus.
Cutting to the surface of the ground when in first bloom, repeating the operation if the plants recover and put forth new buds.