Leersia hexandra
Poaceae tribe Oryzeae
clubhead cutgrass, southern cutgrass, swamp rice grass
25-150 cm tall, 1-1.5 mm thick, decumbent, rooting at the nodes, terminal portions erect, often floating, branched or unbranched;
nodes pubescent, adjacent portions of the internodes glabrous or coarsely scabrous.
annual, 20-500 cm tall, aerenchymatous, sometimes floating.
glabrous or coarsely scabrous, margins often ciliate;
ligules 1-3 mm;
blades 5-25 cm long, 3-15 mm wide, ascending, glabrous or pubescent.
aerenchymatous;
auricles present or absent;
ligules membranous or scarious, sometimes absent;
pseudopetioles sometimes present;
blades with parallel veins, cross venation not evident;
abaxial blade epidermes with microhairs and transversely dumbbell-shaped silica bodies;
first seedling leaf without a blade.
5-15 cm, exserted at maturity, with 1(2) branches per node;
branches 3-10 cm, appressed to ascending, spikelet-bearing to near the base, spikelets appressed to slightly divergent, slightly imbricate.
usually panicles, sometimes racemes or spikes;
disarticulation below the spikelets, not occurring in cultivated taxa.
3.2-4.7(5) mm long, 0.5-2 mm wide, ovate to elliptic.
laterally compressed or terete, with 1 bisexual or unisexual floret, sometimes with 2 sterile florets below the sexual floret, these no more than 1/2 (9/10) the length of the fertile floret;
unisexual spikelets in the same or different panicles;
rachillas not prolonged.
absent or highly reduced, forming an annular ring or lobes at the pedicel apices;
sterile florets 1/8 – 1/2 (9/10) as long as the spikelets;
fertile lemmas 3-14-veined, membranous or coriaceous, apices entire, unawned or with a terminal awn;
paleas similar to the lemmas, 3-10-veined, 1-keeled;
lodicules 2;
anthers usually 6(1-16);
styles 2, bases fused or free, stigmas linear, plumose.
about 2 mm, usually not developed.
usually caryopses, sometimes achenes, ovoid, oblong, or cylindrical;
embryos of the F+FP or F+PP type, small or elongate, with or without a scutellar tail;
hila usually linear, x = 12, 15, 17.
ciliate on the keels and margins, short hispid or glabrous elsewhere, apices acute to acuminate;
paleas ciliate on the keels;
anthers 6, 2-3.2 mm.
= 48.
Leersia hexandra
Poaceae tribe Oryzeae
Leersia hexandra is found in wet areas, usually in fresh water along streams and ponds, where it sometimes forms floating mats. It grows in the southeastern United States and throughout much of the neotropics; the California record probably represents a recent introduction.
Leersia hexandra is sometimes a weed in rice. It usually flowers in late fall, but may flower throughout the year. Very little seed is set.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
The Oryzeae include about 10-12 genera and 70-100 species. Its members are native to temperate, subtropical, and tropical regions. Oryza sativa is one of the world's most important crop species. Four genera are native to the Flora region; two are introduced.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Lemma margins free; fruits achenes, ellipsoid, obovoid, ovoid or subglobose, beaked with a shell-like pericarp. | → 2 |
2. Lemmas of the pistillate spikelets awned; plants emergent, more than 1 m tall | Zizaniopsis |
2. Lemmas of the pistillate spikelets unawned; plants emergent and less than 1 m tall or submerged aquatics | Luziola |
1. Lemmas and paleas clasping along their margins; fruits caryopses, cylindrical or laterally compressed, not beaked. | → 3 |
3. Spikelets unisexual; caryopses terete | Zizcmia |
3. Spikelets bisexual; caryopses laterally compressed or terete. | → 4 |
4. Sterile florets present below the fertile floret, 1/8 – 1/2 (9/10) as long as the spikelets | Oryza |
4. Glumes absent. | → 5 |
5. Leaf blades aerial, not pseudopetiolate, linear to broadly lanceolate; spikelets pedicellate, without stipelike calluses; lemmas unawned; widespread native species | Leersia |
5. Leaf blades floating, pseudopetiolate, elliptic to ovate or ovate-lanceolate; spikelets on stipelike calluses (1)2-10 mm long; lemmas awned; aquatic ornamental species, not known to be established in the Flora region | Hygroryza |
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