A stout handsome plant, with large, wavy leaves and round heads of purple flowers. It is enclosed in a globular involucre of long stiff scales with hooked tips, the scales being also often interwoven with a white, cottony substance.
The whole plant is a dull, pale green, the stem about 3 to 4 feet and branched, rising from a biennial root. The lower leaves are very large, on long, solid foot-stalks, furrowed above, frequently more than a foot long heart-shaped and of a grey colour on their under surfaces from the mass of fine down with which they are covered. The upper leaves are much smaller, more egg-shaped in form and not so densely clothed beneath with the grey down.
The plant varies considerably in appearance, and by some botanists various subspecies, or even separate species, have been described, the variations being according to the size of the flower-heads and of the whole plant, the abundance of the whitish cottonlike substance that is sometimes found on the involucres, or the absence of it, the length of the flower-stalks, etc.
The flower-heads are found expanded during the latter part of the summer and well into the autumn: all the florets are tubular, the stamens dark purple and the styles whitish. The plant owes its dissemination greatly to the little hooked prickles of its involucre, which adhere to everything with which they come in contact, and by attaching themselves to coats of animals are often carried to a distance.
When applied externally as a poultice, the leaves are highly resolvent for tumours and gouty swellings, and relieve bruises and inflamed surfaces generally. The bruised leaves have been applied by the peasantry in many countries as cataplasms to the feet and as a remedy for hysterical disorders.
From the seeds, both a medicinal tincture and a fluid extract are prepared, of benefit in chronic skin diseases. Americans use the seeds only, considering them more efficacious and prompt in their action than the other parts of the plant. They are relaxant and demulcent, with a limited amount of tonic property. Their influence upon the skin is due largely to their being of such an oily nature: they affect both the sebaceous and sudoriferous glands, and probably owing to their oily nature restore that smoothness to the skin which is a sign of normal healthy action.