17. Juncus nodosus L. (knotted rush)

Pl. 95 c, d; Map 374

Aerial stems mostly 10–40 cm tall, produced from the nodes of cordlike, light-colored rhizomes that produce few tuberous thickenings . Leaves with the auricles at the top of the sheaths 0.5–1.0 mm long, hard and often light yellow, rounded, the leaf blades 3–30 cm long, 0.5–1.5 mm wide, tubular and hollow, circular in cross-section, with cross-partitions at regular intervals. Basal leaf usually 1, with a leaf blade. Leaves of the aerial stems 2–4. Inflorescences racemes or few-branched panicles, the branches ascending or spreading, the leaflike bract at the base as long as or usually longer than the inflorescence. Flower clusters 2–15 per inflorescence, spherical, each with (5–)10–25 flowers. Flowers lacking a pair of closely subtending bracts. Perianth 2.5–3.9 mm long, the sepals 2.5–3.5 mm long, slightly shorter than to about as long as the petals, linear-lanceolate, the tips attenuate. Stamens 6 per flower. Fruits 3.5–4.5 mm long, slightly longer than the perianth, narrowly lanceolate in outline, tapering to a long beak, 1-locular. Seeds 0.4–0.5 mm long, one or both ends with short, dark points. 2n=40. July–September.

Uncommon, known only from historical collections from Jackson County (U.S., Canada). Sandbars and bottomland prairies along the Missouri River.