Perennials, mostly 40-150 cm. Stems 1-2+ (ridged), erect, branched distally (glabrous or sparsely hairy). Leaves basal (soon withering) and cauline; petiolate or sessile; blades broadly oblong or oval to elliptic, 4-20 × 2-10 cm, pinnately lobed (rachises ± winged, primary lobes 4-10 pairs, lance-linear to lanceolate or narrowly elliptic, often pinnately lobed or toothed), ultimate margins dentate, faces glabrous or sparsely hairy, gland-dotted. Heads 20-200 in compact, corymbiform arrays. Involucres 5-10 mm diam. Receptacles convex to conic, epaleate. Ray florets 0 (heads disciform, peripheral pistillate florets ca. 20; corollas yellow, lobes 3-4). Disc corollas 2-3 mm. Cypselae 1-2 mm, 4-5-angled or -ribbed, gland-dotted; pappi coroniform, 0.2-0.4 mm. 2n = 18. Flowering Jul-Sep. Disturbed sites (often moist), abandoned plantings; 10-1600 m; introduced; Alta., B.C., Man., N.B., Nfld. and Labr (Nfld.), N.S., Ont., N.W.T., P.E.I., Que., Sask.; Alaska, Ariz., Ark., Calif., Colo., Conn., Ga., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., R.I., S.Dak., Tenn., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.; Eurasia; widely introduced in New World and Old World. Tanacetum vulgare escapes from and/or persists after cultivation. In the flora area, it is naturalized mostly in the northeastern and Pacific Coast states and provinces and sporadically elsewhere.

Plant: Perennial, coarse, aromatic, glabrous to sparsely hairy; rhizome stout, creeping; stems < 1 m, ridged, leafy, branched Leaves: alternate, 4-10 cm, ovate in outline, sessile or short-petioled, pinnately divided; primary leaf divisions generally 4-10 pairs, lanceolate, regularly toothed or lobed, gland-dotted INFLORESCENCE: primary inflorescence a head, each resembling a flower; heads disciform, < 70 in a much divided, generally flat-topped cluster; phyllaries in 3 series, outermost lanceolate, inner oblong; receptacle convex to conic, generally dotted with tubercles Flowers: Pistillate flowers: many; corollas tubular or with inconspicuous to well developed ligules, 3-4-lobed, yellow; Disk flowers: many; corollas 2-3 mm, yellow, tubular; anther tips ovate, bases rounded or ± cordate; style branches truncate with shrub-like tips Fruit: achenes, 1 mm, 5-angled, gland-dotted, generally 3-10-ribbed; pappus a narrow-toothed crown Misc: Escape from cultivated in disturbed, generally urban areas