Annuals or perennials, 50-150+ cm (often rhizomatous). Stems erect, branched distally. Leaves all or mostly cauline; opposite; petiolate (petioles often ± winged, often with connate-perfoliate basal appendages); blades (pinnately nerved) deltate or rounded-rhombic to cordate or ovate, often raggedly pinnately lobed (lobes 3-11), ultimate margins coarsely toothed to denticulate or entire, faces pilose or pilosulous to hirtellous, or glabrate, or glabrous, gland-dotted and/or stipitate-glandular. Heads usually radiate, rarely ± disciform, (2-5+) in loose to congested, corymbiform clusters. Calyculi 0. Involucres hemispheric, 4-15+ mm diam. Phyllaries persistent, 6-21+ in 2 series (distinct, outer 2-6 ovate to linear, ± herbaceous, inner ovate to lanceolate, subequal to or shorter than outer, more scarious, similar to paleae). Receptacles flat to convex, paleate (paleae obovate to oblanceolate or spatulate, herbaceous to scarious). Ray florets 2-6, pistillate, fertile; corollas pale yellowish to whitish (tubes pilosulous, laminae ± cuneate to linear, 3-lobed, sometimes absent or nearly so). Disc florets 12-30+, functionally staminate; corollas pale yellow, tubes shorter than abruptly dilated throats, lobes 5, deltate to lance-ovate. Cypselae plumply pyriform, ± obcompressed, 3-6-angled or -ribbed, finely striate between ribs (narrowed at bases, patently inserted on receptacles, often minutely beaked), sparsely hirtellous or glabrate; pappi 0. x = 15.
Heads radiate or disciform; invol a single series of green bracts; outer fls pistillate and fertile, the cor with or without an expanded, yellow to white ray; receptacle flat or nearly so, chaffy throughout, the bracts subtending the pistillate fls larger and more herbaceous than those of the disk; disk-fls sterile, with undivided style; ray-achenes thick, not much compressed, glabrous or shortly hairy distally; pappus none; perennial herbs (ours) or shrubs with large, opposite (or the upper alternate) lvs and several to many medium- sized subhemispheric heads. 20, New World.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
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