1. Leucanthemum vulgare Lam. (ox-eye daisy, white daisy)

L. vulgare var. pinnatifidum (Lecoq & Lamotte) Moldenke

Chrysanthemum leucanthemum L.

C. leucanthemum var. pinnatifidum Lecoq & Lamotte

Pl. 224 i, j; Map 952

Plants perennial herbs, with rhizomes. Stems 20–90 cm long, erect or ascending, unbranched or few-branched from near the base, finely ridged, sometimes finely hairy toward the tip when young, glabrous or nearly so at maturity. Leaves alternate and basal (basal leaves sometimes withered by flowering time), the basal and lowermost stem leaves long-petiolate, grading abruptly to sessile leaves along most of the stem. Leaf blades 1–12 cm long, narrowly obovate to oblong-oblanceolate; the uppermost sometimes linear, usually pinnately lobed (the lobes sometimes few-toothed) but sometimes only with coarse, narrow, rounded teeth; the main leaves usually clasping the stem and often with stipulelike lobes or teeth toward the base, rounded at the tip, the surfaces glabrous or nearly so, the lobes or teeth 7 to numerous, generally with 1 main vein. Inflorescences of solitary heads at the stem tips, the upper portion of the stem leafless. Heads radiate. Involucre 7–9 mm long, cup-shaped to broadly cup-shaped, the bracts more or less in 3 loosely overlapping series, subequal (the innermost slightly elongate), lanceolate to narrowly ovate-triangular, bluntly to sharply pointed (sometimes rounded on the innermost) at the tip, glabrous, green to yellowish green, the midrib not keeled, the margins purple to brown, at least the margins and tip of the innermost bracts also thin and papery. Receptacle somewhat convex to nearly flat, usually hollow, naked. Ray florets 15–35, pistillate, the corolla 10–20 mm long, white. Disc florets perfect, numerous, the corolla 2.5–3.0 mm long, yellow, glabrous, the 5 lobes without resin canals, persistent, the tube not flattened toward the tip or becoming swollen at fruiting. Pappus absent. Fruits 2.0–2.8 mm long, narrowly obovoid to nearly cylindrical, more or less circular in cross-section, truncate at the base and tip, with usually 10 rounded, light tan to white ribs, the surface otherwise glabrous, dark brown to nearly black and sometimes with minute, short, white lines. 2n=18 (36, 54, 72). May–August.

Introduced, scattered to common throughout the state (native of Europe, Asia, introduced throughout the U.S. and Canada, south to Mexico, Central America, South America). Upland prairies, glades, tops of bluffs, savannas, and openings of mesic to dry upland forests; also pastures, old fields, fallow fields, fencerows, railroads, roadsides, and open, disturbed areas.

Plants with the leaves deeply lobed have been called var. pinnatifidum, which is the common phase of the species in Missouri. Uncommonly seen plants with the leaves more entire are var. vulgare. However, these morphological extremes appear to grade into one another.

Ox-eye daisy is an aggressive rhizomatous colonizer that is difficult to control in gardens and that escapes readily. Although it is a beautiful wildflower, land managers in many states, particularly in the East and Midwest, consider it a problem invasive exotic species. It appears to increase in abundance in upland prairies that are hayed annually and to decrease when these same prairies are subjected to frequent prescribed burns.