Annuals, 15-150 cm. taprooted. Stems 1-3. erect. simple or distally branched (hollow), glabrous. Leaves basal and cauline; basal petiolate or sessile, blades oblong to oblanceolate, pinnately lobed (lobes broad or narrow); cauline sessile, sometimes auriculate clasping, distal smaller, becoming entire and bractlike. Heads (erect) borne singly (at ends of branches) or in open, paniculiform arrays. Involucres cylindro-conic, (4-)6-15+ mm diam. Calyculi of 8-14, spreading to reflexed, unequal bractlets (lengths to ¹/2 phyllaries). Phyllaries 7-20 in 1 series. linear-lanceolate, ± equal, margins scarious, apices acuminate. Receptacles flat, smooth, glabrous, epaleate. Florets 15-30; corollas white, sometimes with rose or purplish veins abaxially (outer surpassing phyllaries). Cypselae tan to mottled grayish brown, fusiform, 9-18(-20) mm, bodies tapering to beaks, ribs or ridges 5, outer usually with antrorse hairs or papillate or scaly indument, inner mostly smooth to cross-rugulose, glabrous; pappi (borne on small discs) ± persistent, of 5-21, white or sordid, ± plumose (at least proximally, barbs sometimes entangled) bristles in 1 series. x = 8.