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.
From Flora of Indiana (1940) by Charles C. Deam
This plant is now found throughout the state. I can remember when it was very rare or absent in northern Indiana, but it has now become well established in all parts, especially on washed slopes in pastures. It is a common weed in the southern part of the state, especially in the worn-out fields and pastures of the limestone area. Not common in the southwestern counties. Clapp, in 1852, writes "Rare in the vicinity of New Albany." J. M. Coulter, in 1875, writes: "Is becoming more abundant (in Jefferson County) every year and almost takes possession of certain old pastures." On account of its showy flowers it has been much cultivated and I believe its spread can be, for the greater part, attributed to this cause. I have never seen the typical form of the species.
Rhizomatous perennial 2-8 dm, simple or nearly so, glabrous or inconspicuously hairy; basal lvs oblanceolate or spatulate, 4-15 cm (petiole included), crenate and often also ±lobed or cleft, the cauline reduced and becoming sessile, deeply and distantly blunt-toothed or sometimes more closely toothed or subentire; heads solitary at the ends of the branches, naked-pedunculate, the disk 1-2 cm wide; rays 15-35, white, 1-2 cm; achenes terete, ca 10- ribbed; x=9; typically diploid, sometimes polyploid. Fields, roadsides, and waste places; native of Eurasia, naturalized throughout most of temp. N. Amer. May-Oct. (Leucanthemum l.; L. vulgare)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.