Sawtooth Sunflower (Helianthus grosseserratus)

Sawtooth Sunflower (Helianthus grosseserratus) 

Sawtooth sunflower is a tall, native perennial common in prairies, meadows, and open roadsides. In good sun and moderately drained soils it can reach eight to twelve feet, rising on smooth stems that often show reddish or purplish tones. The flower heads are bright yellow and daisy-like, usually two and a half to four inches across, with ten to twenty rays surrounding a flat to gently domed disk of small tubular florets. These heads form loose clusters at the ends of branching stems late in summer.

The leaves are long and lance-shaped, typically four to twelve inches long and one to four inches wide. Lower leaves are mostly opposite; upper leaves shift to alternate. The upper surface is medium to dark green and rough, while the underside is paler and softly hairy. The margins are sharply toothed, giving the plant its common name. Sawtooth sunflower favors full sun and open ground, and its height and late-season bloom make it a strong contributor to pollinator activity in tall grass habitats.

Sources:

Illinois Wildflowers

USDA Plants Profile

Flora of North America

Minnesota Wildflowers

(SF)