Cyperus rotundus
Cyperus fendlerianus
chaguan humatag, coco-grass, nutgrass, pakopako, purple nut-sedge
Fendler flatsedge, Fendler's flatsedge, Fendler's nutgrass, Fendler's sedge
trigonous, 10–35(–40) cm × 0.7–3.4 mm, basally indurate, glabrous.
trigonous, (7–)20–70(–85) cm × (0.5–)1–1.8(–2.6) mm, glabrous or sparsely to densely scabridulous on surfaces or on angles immediately proximal to inflorescence in distal 3–6 cm.
V-shaped to flanged V-shaped, 5–30 cm × 2–6 mm.
2–3, flat to V-shaped, (12–)20–40(–55) cm × (2–)3–5(–7) mm.
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 (1–)3–4(–6), largest erect, others at base of central spike, erect spike sessile, loosely to densely cylindric to ovoid-cylindric, (12–)18–30 × (6–)12–20 mm, remaining spikes 1/2 as large;
rays absent;
bracts (2–)3–6(–10), ± horizontal to reflexed parallel to culm, (2–)6–16(–25) cm × (1.5–)2–4(–7) mm;
rachilla ± deciduous, wingless.
(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.
(8–)15–30, spreading to ascending-appressed, oblong-lanceoloid, quadrangular, slightly compressed, 5–8(–10) × (2–)2.4–3.4(–4.2) mm;
floral scales (2–)4–6(–8), yellowish, reddish, or greenish brown, medially greenish, straight to excurved, laterally (2–)3–4(–5)-ribbed, medially (1–)3–(–5)-ribbed, ovate-orbiculate, 2.4–2.8(–3.4) × 2.4–2.8(–3.4) mm, apex obtuse, mucronate to cuspidate, stout, (0.1–)0.3–0.6 mm, medially glabrous.
anthers 1–2.5 mm, styles 1.3–3.5 mm, stigmas (1.8–)2–3.3 mm.
anthers 0.4–0.8 mm;
styles 0.7–1.3 mm;
stigmas 0.7–1.2 mm.
black, sessile, ellipsoid, abaxial face convex, adaxial face concave, 1.4–1.7(–1.9) × 0.8–1 mm, apex obtuse, surfaces puncticulate.
finely reticulate, brown to reddish brown, ± stipelike, obovoid, 1.6–1.9 × 1.1–1.4(–1.6) mm, base attenuate to cuneate, 0.1–0.2 × 0.2 mm, apex obtuse, apiculate, surfaces glabrous.
Cyperus rotundus
Cyperus fendlerianus
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.)
Hybridization between Cyperus fendlerianus and C. sphaerolepis occurs occasionally in the southwestern United States and northern Mexico (B. G. Marcks 1972). The unnamed hybrid appears to be fully fertile and can be recognized by morphologic intermediacy.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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