Stellaria media (L.) Vill., common chickweed. Annual, slender–taprooted, several–stemmed at base, prostrate or decumbent to ascending (erect), sometimes with adventitious roots and branching at nodes of prostrate stems, unbranched below inflorescence of ascending to erect stems, 7—40 cm tall; shoots with only cauline leaves, tender and wilting easily.
Stems cylindric, 0.8—2 mm diameter, weak, slightly wider at nodes, internodes 5—80 mm long, long–hairy along an axial line descending from 1 notch between leaf bases, the hairs soft, translucent, curved to wavy or ± kinky, mostly pointing downward; internodes narrowly hollow.
Leaves opposite decussate, simple, petiolate and pair connected by 2 low ledges across node but grading into sessile bracts just below inflorescence, without stipules; petiole < 25 mm long, ± V–shaped in ×–section, sparsely long–ciliate on 1 or both margins; blade ± ovate to broadly elliptic, 3—43 × 1.5—28 mm, flat, thin, rounded to tapered at base (sparsely ciliate), entire, acuminate to acute at tip, pinnately veined with midrib raised on lower surface but lateral veins sometimes obscure, shiny to dull, glabrous.
Inflorescence leafy dichasial cyme, terminal, appearing umbel–like where clustered from close nodes (solitary), or axillary where internodes of inflorescence greatly elongate, 5—many–flowered, bracteate; bracts subtending peduncle 2 and opposite, leaflike but sessile, ovate, to 40 mm long; peduncle typically erect, intermediate branches ascending; bracts subtending lateral branches 2 and opposite; bractlet subtending pedicel absent; pedicel spreading to erect, 1—20 mm long, long–ciliate along an axial line (stemlike), often recurved in fruit; bracteoles absent.
Flower bisexual, radial, 2—5 mm across; sepals 5, unequal, narrowly ovate to lanceolate, 3—5(—6) × 1—1.6 mm, increasing slightly in fruit, green, narrowly membranous on margins, the larger outer sepals soft–hairy or glabrous and ciliate at base, the inner sepals with wider membranous margins on unexposed margins and glabrous; petals (0)5, Y–shaped, 1.5—2.8 mm long, white with colorless base; lobes subequal, narrowly oblanceolate to narrowly lanceolate, 1.2—2.3 mm long; stamens 3(—5 or 8), free; filaments ± 2 mm long, translucent with expanded, greenish base ( nectaries) producing copious nectar; anthers basifixed, strongly dithecal, ± 0.35 mm long, orange–red, longitudinally dehiscent; pollen translucent pale amber; pistil 1, not stalked; ovary superior, ovoid, 1.2—1.5 mm long, green, 1–chambered with 6—12 ovules on an erect, basal placenta; styles 3, recurved, 0.6—0.8 mm long, whitish translucent, papillate along entire length of upper face.
Fruit capsule, dehiscent from tip by 3 valves splitting lengthwise into 6 erect segments, to 12–seeded, ovoid, 3—5 × 2—2.5 mm, valves resembling lanceolate sepals, straw–colored and somewhat scarious.
Seed ± thick kidney–shaped to disc–shaped, 0.9—1.3 mm diameter, ± 0.6 mm thick, reddish or purplish brown, pebbly to warty on lateral faces, papillate in 3 rows along edge.
A. C. Gibson & B. A. Prigge