Color, light purple. Leaves, whitish underneath, rough-hairy above, oblong or lance-shape, bristly toothed, margined, not so deeply cut as some of the species. Heads of flowers, 2 inches across, single at the ends of branches. Involucre-bracts tipped with a dark glandular spot. Very tall, reaching a limit of 10 feet. August and September.
Rough, leafy, much-branched biennials or perennials, in fields and woods from Massachusetts to Minnesota and southward.
Since thistles are protected from grazing cattle by their spiny nature, and since by their plumed seeds they are easily and widely disseminated, they are among the most formidable of weeds, almost impossible to eradicate when well established. Many old fields are a mass of thistles.