Common sunflower Helianthus annuus L.
Family: Asteraceae (Composite family)
Life cycle: Annual
Native status: Native to North America
Habitat: Crop fields, disturbed areas
General description: Erect plant up to 14 ft tall with coarse stems. Lower leaves heart-shaped, upper ovate to lanceolate; margins toothed to entire. Numerous ‘sunflower’ heads produced up to 6” wide.
Key ID traits: Rough stems and leaves, leaves heart-shaped, triangular or lanceolate with long petioles.
Similar species: Common cocklebur seedling resemble those of common sunflower, but sunflower has small ovate cotyledons whereas cocklebur has large lanceolate cotyledons. Stems of cocklebur have dark spots, whereas sunflower's are hairy.
Miscellaneous: There are numerous native Helianthus species, but Helianthus annuus is the only one with weedy tendencies. When sunflower was added to the noxious weed list, a Kansas legislator jokingly proposed opening a hunting season for the goldfinch (common sunflower is the Kansas state flower, the goldfinch is Iowa’s state bird).