L. oryzoides f. inclusa (Wiesb.) Dörfl.

Flowering stems 50–170 cm long, mostly spreading, circular in cross‑section or nearly so. Leaf sheaths roughened with minute stiff, spinelike, downwardly pointed hairs. Leaf blades (3–)10–30 cm long, 6–15 mm wide, the surfaces strongly roughened with minute, stiff, spinelike hairs, the margins noticeably sawtoothed with stiff, spinelike hairs. Inflorescences with the lowermost branches 2–4 per node, with strongly overlapping spikelets. Spikelets 4–7 mm long, 1.5–2.0 mm wide, oblong to narrowly elliptic, 2.5–4.0 times as long as wide, the lemma and palea with an “eyelash‑like” fringe of hairs along the keel and other nerves, otherwise glabrous. Stamens 3. Fruits 3.0–3.5 mm long. 2n=48. June–October.

Scattered to common throughout Missouri (U.S. and adjacent Canada; Europe and Asia). Swamps, bottomland forests, sloughs, marshes, fens, and margins of streams, ponds, lakes, and ditches, often emergent aquatics.

Late‑season inflorescences sometimes remain all or mostly enclosed by the upper leaf sheath. Such plants have been referred to as f. inclusa, but they do not merit taxonomic recognition. Other forms and varieties also have been segregated by some authors (Pyrah, 1969), based on minor differences in spikelet pubescence and degree of stem flaccidness.

For discussion of a possible hybrid between this species and L. lenticularis, see the treatment of that species. Pyrah annotated a specimen from St. Charles County as the hybrid L. oryzoides ¥ L. virginica but did not discuss it in his monograph (Pyrah, 1969). The specimen appears to represent typical L. oryzoides.