Cyperus rotundus
Cyperus ligularis
chaguan humatag, coco-grass, nutgrass, pakopako, purple nut-sedge
Alabama swamp flatsedge
trigonous, 10–35(–40) cm × 0.7–3.4 mm, basally indurate, glabrous.
trigonous, (30–)60–130 cm × 1–4(–9) mm, densely papillose, otherwise glabrous.
V-shaped to flanged V-shaped, 5–30 cm × 2–6 mm.
with cross ribs prominent, V-shaped, 30–100 cm × 5–13(–20) mm, margins, keel incisive with brownish prickles, papillose throughout, margins and midribs harshly scabrid.
spikes 1(–3), broadly ellipsoid, (12–)15–25(–30) × (12–)20–30(–50) mm, rays (3–)4–6(–7), 0.2–10 cm;, bracts (2–)3–5, horizontal to ascending at 45°, V-shaped to flanged V-shaped, 0.5–10 cm × 0.5–4 mm, rachilla persistent, wings 0.5–1 mm wide.
spikes 3–7, densely oblong-cylindric to ± globose, 10–28(–35) × 8–12(–15) mm;
rays 5–12, 1–16 cm, densely papillose;
bracts 5–12, ascending at 30–75°, flat to V-shaped, 4–50(–90) cm × 1–15 mm;
rachilla deciduous, wings persistent, (0.2–)0.3–0.5(–0.6) mm.
(2–)3–7(–12), compressed, linear, 4–40 × 1.3–1.8 mm, floral scales persistent, 6–36(–42), spreading or appressed, purple to reddish brown, with narrow clear border and green midrib, 7–9-ribbed, ovate, (1.8–)2.6–3.4 × 2.2–3 mm, apex obtuse.
20–80, oblong-ellipsoid, ± terete, slightly compressed, 3–7 × 1–2(–2.7) mm;
distal spikelets spreading or ascending;
floral scales (2–)4–7, appressed, clear to brownish, reddish streaked, medially green, 9–11-ribbed, ovate, (2–)2.5–3.3 × 1.2–2.3 mm, apex acute, mucronate.
anthers 1–2.5 mm, styles 1.3–3.5 mm, stigmas (1.8–)2–3.3 mm.
anthers 0.6–0.8 mm, styles 0.5–1 mm;
stigmas 1–2.3 mm.
black, sessile, ellipsoid, abaxial face convex, adaxial face concave, 1.4–1.7(–1.9) × 0.8–1 mm, apex obtuse, surfaces puncticulate.
brown, slightly stipitate, obovoid to broadly ellipsoid, (1.2–)1.5–1.6(–1.7) × 0.6–0.8 mm, apex apiculate, surfaces puncticulate.
Cyperus rotundus
Cyperus ligularis
Cyperus rotundus is documented in Connecticut, Delaware, New York, and Pennsylvania; there is no evidence of persistent populations.
Cyperus esculentus and C. rotundus are the only two species of subg. Cyperus in the New World that produce tuberiferous stolons. The two species also have persistent floral scales and persistent rachillas, a combination of characteristics not found in any other New World species of Cyperus.
Cyperus rotundus is distinguished from other species of the genus in the New World by its open spikes composed of linear reddish spikelets borne on a conspicuous slender rachis. Cyperus rotundus is usually acknowledged to be the world’s worst weed (cf. G. C. Tucker 1987). In the United States, it does not grow north of the mean 1°C January isotherm. Cyperus esculentus (preceding species) is a serious weed in much of the world, especially in cooler regions where the more tropical C. rotundus does not grow. Cyperus esculentus is able to tolerate lower air temperatures (as low as -18°C). The two species apparently differ also in their thermal optima for growth.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
The papillose culms, rays, and leaves of Cyperus ligularis distinguish it from all other North American species of Cyperus.
Reports of Cyperus ligularis from California (G. C. Tucker 1993b) were based on specimens of C. owanii.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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