Perennials, 10-30(-100+) cm. Stems simple or distally branched. Basal leaves: petioles 10-30(-120) mm, expanding into obovate to spatulate blades 12-35(-50+) × 8-20(-30) mm, margins usually pinnately lobed (lobes 3-7+) and/or irregularly toothed. Cauline leaves petiolate or sessile; blades oblanceolate or spatulate to lanceolate or linear, 30-80+ × 2-15+ mm, margins of mid-stem leaves usually irregularly toothed proximally and distally. Involucres 12-20+ mm diam. Phyllaries (the larger) 2-3 mm wide. Ray florets usually 13-34+, rarely 0; laminae 12-20(-35+) mm. Ray cypselae 1.5-2.5 mm, apices usually coronate or auriculate. 2n = 18, 36, 54, 72, 90. Flowering spring-fall. Disturbed places, meadows, seeps, clearings; 0-2000 m; introduced; Alta., B.C., Ont., Que., Sask.; Alaska, Ariz., Ark., Calif., Colo., Conn., Fla., Idaho, Ill., Ind., Iowa, Kans., Mass., Mich., Mo., Mont., Nev., N.Mex., N.Y., N.Dak., Ohio, Okla., Oreg., Pa., S.C., S.Dak., Tenn., Utah, Va., Wash., W.Va., Wis., Wyo.; Europe, widely adventive. Some botanists (e.g., W. J. Cody 1996) have treated Leucanthemum ircutianum de Candolle, with blades of mid and distal cauline leaves oblong to oblong-lanceolate and not ± pinnate at bases, as distinct from L. vulgare.
Plant: perennial; stems from a creeping rootstock, 2-5 dm, erect, stout, sparingly branched, ± glabrous Leaves: alternate, pinnately lobed or toothed; lowermost and middle blades < 12 cm, obovate to spoon-shaped, petiole = blade, wingless; upper cauline leaves shorter, oblong, sessile INFLORESCENCE: primary inflorescence a head, each resembling a flower; heads 3-7 cm diam, radiate, generally long-peduncled, generally solitary; phyllaries in 2-3 series, margins scarious; receptacle generally convex to conic, chaff 0 Flowers: Ray flowers ± 22(0), pistillate; ligules 1-3.5 mm, white; Disk flowers: many; corollas ± 2.5 mm, yellow; anther tips ovate, bases rounded or ± cordate; style branches truncate with shrub-like tips Fruit: achenes, ± 2 mm, 10-ribbed Misc: Escape from cultivated in pastures, disturbed mtn meadows, roadsides, fields; < 2000 m