Annuals. Stems 0 or 1 (erect, 0–5 cm). Leaves mostly erect, sometimes prostrate; petioles not purplish, margins glabrous or ciliate; blades usually oblanceolate to spatulate, rarely linear, 1–25 cm, margins entire or lobed; lobes 2–3 pairs, linear to spatulate, spreading to antrorse, lobules mostly 0, glabrous or densely hairy. Peduncles elongating after flowering, 3–60 cm in fruit, glabrous or glabrate, or basally puberulent and apically hairy to tomentose, sometimes stipitate-glandular. Involucres cylindric to hemispheric, 1–2 cm in fruit. Phyllaries in 2–3 series, green or medially rosy purple, sometimes purple-black spotted or tipped, subequal to unequal, margins glabrous or ciliate, faces usually puberulent to villous, mostly stipitate-glandular, sometimes glabrous; outer erect or spreading, adaxially usually villous to lanate, sometimes glabrous; inner erect, ± elongating after flowering. Receptacles epaleate. Florets 5–100(–300); corollas yellow, tubes 1–5 mm, ligules 2–15 × 1–3 mm; anthers 1–4 mm. Cypselae 7–16 mm, bodies mostly fusiform to obconic, sometimes tumid, 2–5(–10) mm, beaks 5–11 mm, lengths 1–4 times bodies, ribs 0 or alate, straight to strongly undulate, uniform or diminishing proximally; pappus bristles in 2–3 series, 4–9 mm.
B.C., Ariz., Calif., Idaho, Mont., N.Mex., Nev., Oreg., Utah, Wash., nw Mexico (including Guadalupe Island), introduced in Europe (Sweden).
Varieties 3 (3 in the flora).
|1||Ligules 10–15 mm, much surpassing phyllaries; anthers 2–4 mm; leaf blades toothed to lobed, lobes mostly 3–4(–5) pairs||Agoseris heterophylla var. cryptopleura|
|1||Ligules 2–4 mm, subequaling phyllaries; anthers 1–1.5 mm; leaf margins entire, toothed, or lobed, lobes mostly 2–3 pairs||> 2|
|2||Peduncle lengths 0.5–3 times leaves at flowering; leaf blades glabrous abaxially, pubescent adaxially; peduncles mostly glabrate, or apically tomentose||Agoseris heterophylla var. quentinii|
|2||Peduncle lengths mostly 1.5–4.5 times leaves at flowering; leaf blades uniformly glabrous or hairy; peduncles ± glabrate, or apically hairy to villous, sometimes glabrous||Agoseris heterophylla var. heterophylla|