4. Lysimachia nummularia L. (moneywort)

Pl. 510 h; Map 2324

Plants lacking rhizomes. Stems 10–40 cm long or longer, relatively slender, prostrate, creeping, sometimes mat-forming, rooting at the nodes, glabrous, but usually developing scattered, minute, gland-dots with age. Leaves opposite, with a mostly well-differentiated, but short petiole, this 0.2–0.5 cm long, somewhat flattened, narrowly winged, glabrous except for scattered, minute, gland-dots or punctations (these sometimes faint). Leaf blades (0.4–)1.0–2.5 cm long, (0.4–)1.0–2.5 cm wide, circular or nearly so, the bases rounded, rounded or very broadly angled to a bluntly pointed tip, the margins entire, the surfaces with scattered, minute, glandular dots, these orangish brown to reddish brown, sometimes relatively faint, otherwise glabrous, green to yellowish green; secondary veins faint but often evident. Inflorescences axillary from the nodes, of solitary flowers, the flower stalks 1–3 cm long, glabrous. Calyces (4)5-lobed, the lobes 6–9 mm long, narwowly ovate to ovate with a cordate base, gland-dotted, with a slightly thickened midvein. Corollas (4)5-lobed, the lobes 12–15 mm long, obovate, rounded or broadly angled to a bluntly pointed tip, the margins usually slightly uneven or toothed toward the tip, yellow, moderately to densely glandular but lacking reddish markings on the upper surface toward the base, both surfaces with scattered, reddish purple to nearly black glandular spots and short lines. Stamens shorter than the corollas, the filaments 3–5 mm long, slightly unequal, fused basally into a short tube, glandular-hairy. Staminodes absent. Styles 4–5 mm long. Fruits and seeds not produced. 2n=30, 32, 34, 36, 43, 45. May–August.

Introduced, scattered nearly throughout the state, but apparently absent from the Unglaciated Plains and the western half of the Glaciated Plains Divisions (native of Europe, Asia; introduced nearly throughout the U.S. and adjacent Canada, except so far for portions of the Great Plains and Rocky Mountains). Banks of streams, rivers, and spring branches; margins of ponds and lakes, sloughs, acid seeps, and bottomland forests; also lawns, railroads, roadsides, and moist disturbed areas.

This Eurasian species is easily distinguished by its creeping habit and round, punctate leaves. It is sometimes cultivated as a ground cover and several cultivars differing in leaf color exist, however, it can become very aggressive in gardens. It is considered an invasive exotic in some eastern states. In Missouri specimens, fruits apparently are not produced and the species appears to be spreading mainly vegetatively in the state, from stem pieces transported by water, and human-mediated means.