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giant flatsedge, Mexican papyrus

one-flower flatsedge

Habit Herbs, perennial, rhizomatous, stout. Herbs, perennial, cespitose, rhizomatous.
Culms

roundly trigonous, 200–350 cm × 15–50 mm, glabrous.

trigonous, basally tuberous-thickened, (5–)15–40(–80) cm × 1–2.5 mm, glabrous.

Leaves

bladeless.

flat to V-shaped, (5–)10–30(–60) cm × (0.5–)1–3(–4) mm.

Inflorescences

spikes loosely cylindric, 15–40 × 8–16 mm;

rays 5–8, ascending to erect, stiff,20–30 cm; 2d order rays 5–15 cm;

bracts 10–12, ascending at 30–60°, flat, (8–) 20–45 cm × 4–12 mm; 2d order bracts (5–)15–25 cm × 1.5–5 mm;

rachilla persistent, separating laterally, remaining firmly attached basally, wings 0.3–0.4 mm wide.

spike 1, loosely to densely ovoid to cylindric, 8–36 × 8–20 mm;

rays 3–6(–9), (5–)10–32 cm;

bracts 3–6, horizontal to ascending at 30°, V-shaped, (1–)3–15(–30) cm × 0.5–4.5 mm;

rachilla deciduous, wings 0.5–0.7 mm wide.

Spikelets

(15–)50–80, slightly compressed, linear, ± quadrangular, 5–12 × 0.6–1.4 mm;

floral scales 8–20, appressed, reddish beside 5-ribbed green medial part, white to hyaline near margins, ovate, 1.8–2.2 × 1.2–1.5 mm, apex acute to obtuse.

(5–)20–35(–65), linear to oblong (without narrowed basal portion), quadrangular; (2.2–)4–10(–18) × 0.7–1.1 mm;

floral scales persistent, 1–5, appressed, pale greenish white laterally, stramineous with reddish dots, or deep red, greenish or light brown medially, 3–6-ribbed laterally, narrowly ovate to oblong-elliptic, 2.6–3.9 × 1.6–2 mm, apex rounded to ± acute, entire, mucronulate;

distal scale with glabrous midrib and mucro 0.1–0.3(–0.5) mm;

sterile terminal scale of spikelet only 0.4–0.6 mm wide, involute, frequently uncinate.

Flowers

anthers 0.7–1 mm (connective prolonged beyond anther as red subulate appendage 0.2–0.5 mm, its apex sometimes setose);

styles 0.2–0.5 mm;

stigmas (0.8–)1.2–1.8 mm.

anthers (0.3–)0.4–0.6 mm;

styles 0.4–0.5 mm;

stigmas 0.5–0.9 mm.

Achenes

pale brown, sessile, oblong, 0.9–1 × 0.4–0.5 mm, apex scarcely apiculate, surfaces puncticulate.

light brown to reddish brown, sessile or slightly stipitate, ellipsoid, (1.8–)2–2.4 × 0.6–0.8(–0.9) mm, apex slightly apiculate, surfaces puncticulate.

Cyperus giganteus

Cyperus retroflexus

Phenology Fruiting summer. Fruiting mid summer–early fall (Jul–Sep).
Habitat Stream banks, marshes Damp, disturbed soils, croplands
Elevation 0–10 m (0–0 ft) 0–1000 m (0–3300 ft)
Distribution
from FNA
LA; TX; Mexico; Central America; South America; West Indies [Introduced in North America]
[BONAP county map]
from FNA
AL; AR; AZ; MO; MS; NM; OK; TX; Mexico
[WildflowerSearch map]
[BONAP county map]
Discussion

Cyperus giganteus was erroneously reported from Florida, a misidentification of C. papyrus (R. R. Haynes and A. Lasseigne 1969).

Recently, some nurseries specializing in water plants have begun to offer C. giganteus under the name “Mexican papyrus.” Escaped cultivated plants may be expected in southeastern and southwestern United States.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Cyperus retroflexus is distinguished from other species of Cyperus with deciduous spikelets by the involute, sterile terminal scale of the spikelet. In plants with cuspidate scales, the terminal scale is usually somewhat recurved, giving the appearance of a hook at the end of the spikelet.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 23, p. 173. FNA vol. 23.
Parent taxa Cyperaceae > Cyperus > subg. Cyperus Cyperaceae > Cyperus > subg. Cyperus
Sibling taxa
C. acuminatus, C. aggregatus, C. alopecuroides, C. amabilis, C. articulatus, C. bipartitus, C. cephalanthus, C. compressus, C. croceus, C. cuspidatus, C. dentatus, C. dentoniae, C. diandrus, C. difformis, C. digitatus, C. dipsaceus, C. distans, C. distinctus, C. drummondii, C. echinatus, C. elegans, C. entrerianus, C. eragrostis, C. erythrorhizos, C. esculentus, C. fendlerianus, C. filicinus, C. filiculmis, C. filiformis, C. flavescens, C. flavicomus, C. floribundus, C. fugax, C. fuligineus, C. fuscus, C. gracilis, C. granitophilus, C. grayi, C. grayoides, C. haspan, C. hermaphroditus, C. houghtonii, C. hypopitys, C. hystricinus, C. involucratus, C. iria, C. laevigatus, C. lancastriensis, C. lanceolatus, C. lecontei, C. lentiginosus, C. ligularis, C. lupulinus, C. manimae, C. microiria, C. mutisii, C. niger, C. ochraceus, C. odoratus, C. onerosus, C. ovatus, C. owanii, C. oxylepis, C. pallidicolor, C. papyrus, C. parishii, C. pilosus, C. planifolius, C. plukenetii, C. polystachyos, C. prolifer, C. prolixus, C. pseudothyrsiflorus, C. pseudovegetus, C. pumilus, C. reflexus, C. refractus, C. retroflexus, C. retrofractus, C. retrorsus, C. rotundus, C. sanguinolentus, C. schweinitzii, C. serotinus, C. seslerioides, C. setigerus, C. spectabilis, C. sphacelatus, C. sphaerolepis, C. squarrosus, C. strigosus, C. surinamensis, C. tetragonus, C. thyrsiflorus, C. virens
C. acuminatus, C. aggregatus, C. alopecuroides, C. amabilis, C. articulatus, C. bipartitus, C. cephalanthus, C. compressus, C. croceus, C. cuspidatus, C. dentatus, C. dentoniae, C. diandrus, C. difformis, C. digitatus, C. dipsaceus, C. distans, C. distinctus, C. drummondii, C. echinatus, C. elegans, C. entrerianus, C. eragrostis, C. erythrorhizos, C. esculentus, C. fendlerianus, C. filicinus, C. filiculmis, C. filiformis, C. flavescens, C. flavicomus, C. floribundus, C. fugax, C. fuligineus, C. fuscus, C. giganteus, C. gracilis, C. granitophilus, C. grayi, C. grayoides, C. haspan, C. hermaphroditus, C. houghtonii, C. hypopitys, C. hystricinus, C. involucratus, C. iria, C. laevigatus, C. lancastriensis, C. lanceolatus, C. lecontei, C. lentiginosus, C. ligularis, C. lupulinus, C. manimae, C. microiria, C. mutisii, C. niger, C. ochraceus, C. odoratus, C. onerosus, C. ovatus, C. owanii, C. oxylepis, C. pallidicolor, C. papyrus, C. parishii, C. pilosus, C. planifolius, C. plukenetii, C. polystachyos, C. prolifer, C. prolixus, C. pseudothyrsiflorus, C. pseudovegetus, C. pumilus, C. reflexus, C. refractus, C. retrofractus, C. retrorsus, C. rotundus, C. sanguinolentus, C. schweinitzii, C. serotinus, C. seslerioides, C. setigerus, C. spectabilis, C. sphacelatus, C. sphaerolepis, C. squarrosus, C. strigosus, C. surinamensis, C. tetragonus, C. thyrsiflorus, C. virens
Synonyms C. uniflorus var. floribundus, C. uniflorus var. retroflexus, Mariscus uniflorus
Name authority Vahl: Enum. Pl. 2: 364. (1805) Buckley: Proc. Acad. Nat. Sci. Philadelphia. 14: 9. (1862)
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