J. Wash. Acad. Sci. 21: 333. 1931.
Annuals, 25–60 cm. Stems erect, sparsely hispid. Leaves mostly cauline; mostly alternate; petioles 1.2–5 cm; blades ovate to lanceovate, 4.5–13 × 1–4 cm, bases cuneate, margins entire, abaxial faces sparsely hispid, not glanddotted. Heads usually borne singly. Peduncles 4–9 cm. Involucres hemispheric, 20–27 mm diam. Phyllaries 11–23, laceolate to lance-linear or lanceovate, 17–33 × 1–2.9 mm (notably surpassing discs), (margins ± ciliate) apices attenuate, abaxial faces usually sparsely hispid to hispidulous. Paleae 7–8 mm, apices 3-toothed (middle teeth attenuate, apices purplish, ± hispid). Ray-florets 7–12; laminae 18–37 mm. Disc-florets 25+; corollas 6.8–7.5 mm, lobes reddish; anthers dark, appendages dark (style-branches reddish). Cypselae 4.6–9 mm, appressed hairy; pappi of 2 linear scales 2–4.5 mm plus 4–6 scales 1–3.5 mm. 2n = 34.
Phenology: Flowering spring–fall.
Habitat: Sand dunes
Elevation: 1300–1500 m
L. H. Rieseberg (1991) provided evidence that Helianthus anomalus is a hybrid species derived from H. annuus and H. petiolaris, and subsequent work has confirmed and extended that hypothesis.