This native annual plant is 2-8' tall and little branched, except at the top near the inflorescence. The central stem is round and largely hairless, with fine vertical lines that are dark green. The alternate leaves are up to 8" long and 3" across. They are lanceolate, ovate, or oblanceolate, often with pinnate lobes. The upper surface of the leaves is glabrous or has scattered white hairs, while the margins are coarsely serrated or dentate. The lower leaves have short petioles, while the smaller upper leaves are sessile. The upper stems terminate in panicles of flowerheads. A flowerhead consists of numerous tubular disk florets, which are enclosed by green bracts that are smooth and linear. Sometimes these bracts assume a purplish appearance. The corollas of the disk florets, which are barely visible above the bracts, are white. The outer florets are fertile and pistillate, while the inner florets are hermaphroditic or sterile. The flowerheads are about ¾" long and ¼" across; they are slightly wider at the base, where there may be some outer bracts that are very short and linear. The blooming period occurs during late summer or early fall for about a month. There is no floral scent, although the foliage has a rank smell. The achenes develop with tufts of soft white hair; they are dispersed by the wind. The root system is shallow and fibrous.