Plants perennial, with rhizomes. Flowering stems ascending
to spreading, sometimes rooting at the nodes, sometimes branched, circular in
cross‑section or somewhat flattened, glabrous or hairy near the nodes.
Leaves several per stem. Leaf sheaths mostly not overlapping, glabrous or
roughened with minute, stiff, spinelike, downwardly pointing hairs, open for
most of their length, the ligule membranous, glabrous, usually with an uneven
margin. Leaf blades flat, glabrous to hairy, often roughened, with minute,
stiff, spinelike, hairs, especially along the margins. Inflorescences open
panicles with loosely ascending, spikelike branches. Spikelets numerous,
minutely stalked, oriented toward 1 side of the inflorescence branches,
strongly flattened, with 1 perfect floret. Glumes absent (actually reduced to a
minute, cuplike structure at the spikelet base). Lemma 1, strongly keeled,
narrowly to broadly oblong, the tip abruptly tapered to a point but awnless,
papery, glabrous or hairy, sometimes with a noticeable fringe of hairs along
the margins and keel, 5‑nerved. Paleas similar to and about as long as
the lemmas, 3‑nerved. Stamens 2 or 3 (1 or 6 elsewhere). Fruits often
somewhat flattened, uneven in outline, with 1 side nearly straight and the
other curved, reddish brown. Seventeen species, nearly worldwide, most diverse
in tropical regions.
Plants of Leersia are quite variable in size and
habit, depending upon season and habitat. In L. lenticularis and L.
oryzoides, the stiff, needlelike hairs of the leaves, especially along the
margins, act as tiny sawteeth, giving rise to the common name “cutgrass,” as
any person knows who has walked through a stand and been scratched or
lacerated. The leaves of L. virginica are less formidable.