6. Cerastium glomeratum Thuill. (clammy chickweed)

C. viscosum f. apetalum (Dumort.) Mert. & W.D.J. Koch

Map 1455, Pl. 341 b, c

Plants annual. Stems 3.5–30.0 cm long, erect or ascending, sometimes branched above the midpoint, densely pubescent with glandular (especially toward the tip) and nonglandular hairs. Leaves sessile, lacking axillary clusters of leaves. Leaf blades 0.5–3.0 cm long, spatulate (some basal leaves) or elliptic to narrowly oblong-obovate, abruptly short-tapered to a minute, sharp point at the tip. Flowers in dense, crowded clusters or later slightly open clusters or small panicles, the stalks 0.1–0.3 cm long, 0.5–1.0 times as long as the sepals, usually longest in the first-opening flowers, erect or spreading at flowering and fruiting, densely pubescent with mostly short glandular hairs, the bracts with herbaceous, green margins. Sepals 5, (2–)3–5 mm long, lanceolate, green or occasionally reddish-tinged at the tip, angled or tapered to a sharply pointed tip, moderately to densely pubescent with glandular and nonglandular hairs, these extending past and somewhat obscuring the sepal tips. Petals 5 (rarely absent), 3–5 mm long, 0.7–1.2 times as long as the sepals, shallowly 2-lobed at the tip, the veins usually not apparent. Stamens 10. Styles 5. Capsules (3.5–)5.0–9.0 mm long, 1–2 times as long as the sepals, slightly curved. Seeds 0.5–0.6 mm wide, the surface tuberculate, brown. 2n=72. March–July.

Introduced, scattered mostly south of the Missouri River (native of Europe; introduced in the eastern U.S. west to Michigan and Arizona, also Idaho and Nevada west to Washington, Oregon, and California; Canada). Bottomland forests, banks of streams and rivers, ledges and tops of bluffs, and occasionally glades; also crop fields, fallow fields, old fields, ditches, railroads, roadsides, and open, disturbed areas.

Cerastium glomeratum is a common species in disturbed areas, especially in areas to the south and east of Missouri. It was long known as C. viscosum (Steyermark, 1963), a name that has been officially rejected as having ambiguous application (Turland and Wyse Jackson, 1997). The rare form with flowers lacking petals has been called f. apetalum.