1. Sherardia arvensis L. (field madder)

Pl. 551 a–c; Map 2560

Plants annual herbs, glabrous or more commonly minutely roughened or pubescent throughout with wavy, soft hairs, the stem nodes sometimes ringed with dense, short hairs. Stems 5–40 cm long, spreading to loosely ascending from a spreading base, rarely strongly ascending, sometimes forming loose mats, 4-angled. Leaves in whorls of (4)6, sessile or nearly so. Stipules absent. Leaf blades 4–20 mm long, 1.5–3.0 mm wide, narrowly elliptic to nearly linear, angled at the base, angled to a sharply pointed tip, the margins entire, flat to slightly rolled under, glabrous or minutely roughened or hairy, the upper surface glabrous to slightly roughened or sparsely soft-hairy, the undersurface soft-hairy, not glandular, the venation with only the midvein visible. Inflorescences terminal and axillary, of small headlike clusters that are closely subtended by whorls of (4)6 or 8, small, leaflike, involucral bracts. Flowers sessile or nearly so, 2–4 per cluster. Calyces 0.5–1 mm long, minutely 4-lobed, the lobes triangular. Corollas 4.0–5.5 mm long, trumpet-shaped, the slender tube well-developed, longer than the 4 spreading lobes, pink (blue elsewhere), the lobes not overlapping in bud. Stamens 4, attached in the corolla throat, the anthers exserted. Style unequally 2-branched, the stigmas capitate. Ovary fully inferior, 1-locular, the ovules 1 per locule. Fruits schizocarps, 1–2 mm long, 2–4 mm wide, 2-lobed, splitting from the base into 2 mericarps, these globose or nearly so, indehiscent. 2n=22. April–June.

Introduced, scattered in the southern portion of the Ozark and Mississippi Lowlands Divisions (native of Europe, Asia; introduced in the eastern U.S. west to Iowa and Texas, also Washington to California, Nevada, and Arizona, Hawaii; Canada, Mexico). Glades, ledges of bluffs, and banks of streams and rivers; also pastures, cemeteries, lawns, gardens, sidewalks, roadsides, and open, disturbed areas.

Steyermark (1963) knew this weedy species only from a few collections from Barry and Newton Counties. It has become much more widely distributed in southern Missouri since that time.