Helianthus annuus is a coarse annual herb, to 3 m, from fibrous roots, stems very rough-hairy, branched.
Leaves mostly alternate, but upper or lower leaves sometimes opposite, blade 2-30 cm long very rough both sides, broadly egg to heart-shaped, tip pointed, base rounded to lobed, veins palmate at base, margin coarsely, irregularly toothed, stalk long.
Flower heads large, 8-15 cm wide, rays dark yellow, showy, not fertile; disk dark purplish to brown ca 3 cm wide or more, basal bracts of head large, loose, egg-shaped, abruptly narrowed above middle to long-pointed tip, rough, margins with long bristles (ciliate).
Fruit dry, 1-seeded achenes 0.9 cm long, 0.4-0.8 cm wide, grayish with dark stripes; seeds eaten by many birds and small mammals, plants eaten by muskrats (Martin et al. 1951). Winter flower heads with hemispheres of dense chaffy bracts surrounding seeds. Grown commercially for bird seed and seed oil.
Wetland status: FAC-.
Frequency in NYC: Infrequent.
Origin: Midwestern and western N. America.
Habitat: On open soil, especially roadside construction sites, sparsely vegetated, moist fill, soil pH 5.5-7.8 (USDA, NRCS 2007). Escaped from cultivation.
Notes: A commercial crop species.