Helianthus L.

Erect or decumbent annual or perennial herbs. Leaves usually opposite below, often alternate above (all alternate in H. debilis), sessile or petiolate, simple, entire to dentate or serrate, usually with 3 main veins. Capitula usually large, radiate, hemispherical, terminal and solitary or few (rarely numerous) in a cyme, rarely also axillary, on non-fistulose peduncles; involucral bracts herbaceous, 2–4 seriate, subequal, herbaceous, with ribs obscure; receptacle flat or convex; paleae concave or conduplicate, rigid, with an acuminate awn (acumen) and 2 shorter lateral lobes, deciduous, enfolding achenes. Ray florets female, bisexual or male, in 1 row; ligules yellow (rarely orange). Disc florets bisexual, fertile, 5-lobed, brownish, purple, or yellowish. Achenes obovate to oblong, compressed (bluntly 3-or 4-angled). Pappus absent or of 2 or more early-caducous scale-like awns, rarely small persistent scales present.