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Sawtooth sunflower flowerheads are 2.5-4" across with 10-20 bright yellow ray florets and over 100 tubular golden-yellow disc florets with five protruding brown anthers fused around a yellow style with a bifurcated stigma. Behind the flowers are multiple layers of spreading bracts that are pointed with hairy margins, especially near their base. Only the disc florets are fertile; the ray florets are sterile. (This is true throughout the genus Helianthus, although this situation seems more understandable (to me) than the the situation in the genus Silphium, where the opposite is true.) Sawtooth sunflowers can be distinguished from other Helianthus spp. by their hairless, reddish-purple stems; the arching leaves with a longitudinal fold are also characteristic but not definitive.

Helianthus

Helianthus grosseserratus

sawtooth sunflower [Blooms: Jul-Sep]

Jerusalem artichoke should rightly be called a "sunflower" like the other four members of the genus Helianthus present in Jackson Park. Five to fifteen flowerheads ride on hairy peduncles up to 8" long and are 2.5-3.5" across; each is cupped by 2-3 overlapping series of phyllaries (bracts) that are more triangular than lance-shaped, hairy, and sharply pointed. The flowerheads consist of 10-20 sterile, yellow ray florets; the 60+ fertile disc florets consist of tubular yellow corollas about 1/4" long with five lobes at their apex and five protruding brown or black anthers fused around a yellow style with a bifurcated stigma. Jerusalem artichoke was cultivated by the indigenous peoples of the midwest for its tasty and carbohydrate-rich tubers.

Helianthus

Helianthus tuberosus

Jerusalem artichoke [Blooms: Aug – Oct]