Cyperus rotundus
Cyperus articulatus
chaguan humatag, coco-grass, nutgrass, pakopako, purple nut-sedge
jointed flatsedge, priprioca
trigonous, 10–35(–40) cm × 0.7–3.4 mm, basally indurate, glabrous.
to 25 cm apart, 1(–3) together, terete (scarcely compressed in drying), occasionally trigonous for apical 1/3, 40–140(–200) cm, 4–12 mm thick at base, (1.2–)1.5–2.5 mm thick at apex (with conspicuous transverse septa ca. 3 cm apart basally, to 3–5 mm apart apically), glabrous or infrequently scabrid on angles apically;
sheaths at base of culm, 2–3, (5–)10–25 cm, loose, papery.
V-shaped to flanged V-shaped, 5–30 cm × 2–6 mm.
usually bladeless, blades when present, cross ribs prominent, especially adaxially, (1–)10–20(–40) cm × 4–6(–9) 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(–5), broadly ovoid to ± umbellate, 15–45 × 10–30 mm;
rays 5–7(–10), 0.3–8(–12) cm; 2d order rays occasionally present, 5–20 mm;
bracts 2(–4), erect, longest appearing to be continuation of culm, deltate to lance-linear, 0.2–2(–9) cm × 1.5–4.5 mm;
rachilla persistent, wings translucent, whitish, or stramineous, 0.4 mm wide.
(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.
(1–)5–10, linear, compressed, 10–35(–45) × 1.1–2 mm;
floral scales deciduous, 15–45, spreading or appressed, laterally light brown, medially green to brown, laterally 1–2-ribbed, medially 3-ribbed, oblong-elliptic to ovate, 2.9–3.7 × 1.1–1.6(–1.8) mm, apex acute.
anthers 1–2.5 mm, styles 1.3–3.5 mm, stigmas (1.8–)2–3.3 mm.
anthers 1.7–2.4 mm;
styles 1.2–3.6 mm;
stigmas 1.7–6 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, stipitate, obovoid-ellipsoid, 1.2–1.6 × 0.4–0.6 mm, stipe 0.1 mm, apex markedly apiculate, surfaces puncticulate.
Cyperus rotundus
Cyperus articulatus
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.)
In habit, Cyperus articulatus is reminscent of larger plants of Juncus or Schoenoplectus and is the only North American Cyperus with such a reedlike appearance.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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