COMMON SUNFLOWER, Helianthus annuus L. 1, upper stem with flowers; 2, lower stem and root system; 3, seed; 4, distribution. Annual, reproducing only by seed. Root system fibrous. Stem erect, stout, rough, 2 to 10 feet (0.6 to 3 m) tall, freely branching. Leaves alternate, simple, rough, hairy, mostly with saw-toothed margins; lower ones long-petioled. Flower heads 1 to 5 inches (2.5 to 12.5 cm) in diameter. Ray flowers yellow, surrounding brown or reddish-brown disk flowers. Seed 1/8 to nearly 1/2 inch (0.3 to 1.3 cm) long, ovate to wedge-shaped, slightly 4 angled and flattened, white, or gray or dark brown with lighter stripes or spots, without hairs except at the tip. Found in cultivated land, pastures, and waste places.

 PRAIRIE SUNFLOWER, Helianthus petiolaris Nutt. 5, distribution. Similar to the above but smaller and more slender. Annual. Stems 6 inches to 6 feet (15 cm to 1.8 m) tall, rough. Leaves usually pale green, simple, slender, petioled, rough on both sides, all but lowest alternate. Flower heads 1 to 2 inches (2.5 to 5 cm) in diameter. Found in dry prairies and uncultivated land.