This is a native annual wildflower with a large and stout central stem about 3-9' tall, although occasionally smaller. Toward the apex of the plant, there may be a few side stems, but it is tall and columnar overall. The central stem is light green to reddish green, terete, and covered with stiff spreading hairs. The large alternate leaves are up to 8' long and 6' across they have a tendency to droop downward from the long petioles. They are cordate, ovate-cordate, or ovate with fine dentate margins, although some of the small upper leaves may have smooth margins and a lanceolate shape. The upper surface of the leaves is dull green and covered with short stiff hairs, providing it with a sandpapery feel. The petioles are light green to reddish green, and covered with short stiff hairs; the upper surface of each petiole is channeled. The daisy-like flowerheads consist of numerous central disk florets (each about 1/8' across) that are yellow to brown; they are surrounded by approximately 20-40 ray florets. The petal-like extensions of the ray flowers are yellow. Each flowerhead is about 3-5' across. At the bottom of each flowerhead, there are large overlapping bracts in 2-3 series. These floral bracts are dull green, stiffly hairy, and ovate in shape, tapering abruptly to form long narrow tips. An average plant will bear from 1-12 of these flowerheads, and bloom from mid- to late summer for about 1½ months. There is not much of a fragrance, although the florets have a musty smell that is peculiar to sunflowers. During the fall, the disk florets are replaced by large seeds that are ovoid and somewhat flattened in shapee; they are dispersed by gravity when the tall plants topple over during the winter. Like many other species in its genus, the Annual Sunflower exudes chemicals that kills off other kinds of vegetation. Thus, it has a tendency to form colonies that exclude other plants, particularly in disturbed areas.