Plants erect, (3-)50-200(-350+) cm, branched mostly distally. Leaves: faces usually glabrate (proximal margins ± ciliolate, hairs usually stiff, spreading and hispid on nerves, hairs erect); proximal blades oblanceolate to linear, 20-50(-100+) × 4-10(-15+) mm, toothed to entire; distal similar, smaller, entire. Heads usually in paniculiform, sometimes corymbiform arrays. Involucres 3-4 mm. Phyllaries usually glabrous, sometimes sparsely strigose (margins chartaceous to scarious); outer greenish to stramineous, lanceolate to linear, shorter; inner stramineous to reddish, lance-attenuate to linear. Receptacles 1-1.5(-3) mm diam. in fruit. Pistillate florets 20-30(-45+); corollas ± equaling or surpassing styles, laminae 0.3-1 mm. Disc florets 8-30+. Cypselae uniformly pale tan to light gray-brown, 1-1.5 mm, faces sparsely strigillose; pappi of 15-25, white bristles 2-3 mm. 2n = 18. Flowering year round, mostly summer-fall. Disturbed places; 0-2000 m; Alta., B.C., Man., N.S., Ont., P.E.I., Que., Sask.; Ala., Ariz., Ark., Calif., Colo., Conn., Fla., Ga., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., R.I., S.C., S.Dak., Tex., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.; Mexico; Central America; introduced in South America, Europe, Asia, Africa. Conyza canadensis is thought to be native to North America and is now widely adventive, e.g., in South America, Europe, Asia, and Africa. Plants with stems glabrous and phyllaries red-tipped are sometimes treated as var. pusilla; similar plants with stems glabrous and phyllaries stramineous (not red-tipped) are sometimes treated as var. glabrata.

Plant: Taprooted annual forb to 1 m; stems unbranched below, branched above, strigose or stiff-spreading-hairy Leaves: leaves alternate, linear-lanceolate, 2-8 mm wide, 3-6 cm long, entire, glabrous to strigose, often ciliate INFLORESCENCE: primary inflorescence a head, each resembling a flower; heads obscurely radiate; lateral clusters not overtopping central; fresh involucre generally 2.5-4 mm diam; phyllaries 1-3.5 mm, glabrous to strigose, midvein resin-filled, orange when dry Flowers: Pistillate flowers 20-40; corollas 2.5-3 mm, white, pink, or cream, narrowly cylindric; ligule < 1 mm; Disk flowers 7-13; corollas 2.5-3 mm, yellow, lobes short-triangular; style tips lanceolate, included or short-exserted Fruit: ± 1.5 mm, elliptic, compressed, puberulent; pappus 2.5-3 mm, generally whitish in age Misc: Waste ground; generally < 2000 m; Jun-Sep Notes: heads obscurely radiate, appearing discoid References: Jepson Manual, Arizona Flora, ASU specimens