Annuals, biennials, or perennials [subshrubs, shrubs, trees], (0.5–)2–90(–100) cm (taprooted, fibrous-rooted, or rhizomatous and fibrous-rooted, sometimes with simple or branched caudices, sometimes stoloniferous). Stems erect to ascending, decumbent, or prostrate, simple or branched, glabrous or hairy, sometimes glandular (hairs 2-seriate, minute, sometimes stipitate). Leaves basal and/or cauline (basal persistent or not to flowering); alternate; sessile or petiolate; blades 1-nerved (3-nerved), linear to lanceolate, oblanceolate, or spatulate (bases sometimes clasping), margins entire or ± dentate to pinnatifid, faces glabrous or hairy, sometimes glandular. Heads usually radiate, sometimes discoid or disciform (erect, nodding, or arching-pendent in bud), borne singly or in loose, corymbiform or paniculiform arrays. Involucres turbinate to hemispheric, 5–35 mm diam. Phyllaries 30–125(–150) in 2–5 series, 1- or 3-nerved (nerves golden-resinous; usually flat, rarely broadly keeled to convex), narrowly elliptic- to linear-lanceolate, unequal to equal, margins scarious or not, faces hairy or glabrous, sometimes glandular. Receptacles flat to conic, pitted, epaleate. Ray florets 0 or 12–350 in 1(–2+) series, pistillate, fertile; corollas usually white to bluish or purplish to pink, less commonly yellow (coiling from apices, reflexing at tube/lamina junction, or remaining ± straight and spreading). Peripheral florets (disciform heads) 50–200 in 1–4 series, pistillate. Disc florets 25–450, bisexual, fertile; corollas yellow (nerves orange-resinous), tubes shorter than usually tubular, sometimes strongly inflated and indurate throats, lobes 5, erect to spreading, deltate; style-branch appendages mostly deltate (papillate). Cypselae (tan) oblong to oblong-obovoid, compressed to flattened, 2(–4)-nerved, or subterete, 5–14-nerved (sect. Wyomingia and some other species), faces glabrous or strigose or sericeous, eglandular; pappi persistent or readily falling, usually of outer setae or scales (0.1–0.4 mm), sometimes connate, plus 5–40(–50), stramineous, barbellate bristles, sometimes pappi only on ray or only on disc cypselae, or 0. x = 9.