Cyperus rotundus
Cyperus aggregatus
chaguan humatag, coco-grass, nutgrass, pakopako, purple nut-sedge
ballast sedge, inflated-scale flatsedge
trigonous, 10–35(–40) cm × 0.7–3.4 mm, basally indurate, glabrous.
trigonous, 20–100 cm × 0.8–2.5 mm, glabrous.
V-shaped to flanged V-shaped, 5–30 cm × 2–6 mm.
5–10, V-shaped to flanged V-shaped, 10–70(–90) cm × 2–7 mm, margins and midribs scabridulous or glabrous.
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(–6), densely cylindric, 6–30 × 5–11 mm;
rays 3–12, 0.4–5(–7) cm;
rays and rachis glabrous; usually only 1–2 spikes of inflorescence on elongate rays, other spikes sessile or nearly so;
bracts 4–7, horizontal to slightly ascending, 1–16 cm × 0.5–4 mm;
rachilla deciduous, wings persistent, 0.5 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.
20–80, ellipsoid, roughly quadrangular, 3–5 × 1–1.4 mm;
floral scales 1–2(–4), appressed, stramineous to golden brown, often red-speckled, medially greenish, 9-ribbed, elliptic to ovate, 2.4–3.4 × 1.8–2.6 mm, apex obtuse.
anthers 1–2.5 mm, styles 1.3–3.5 mm, stigmas (1.8–)2–3.3 mm.
anthers 0.4–0.6 mm;
styles 0.7–1.1 mm;
stigmas 1.4–2.1 mm.
black, sessile, ellipsoid, abaxial face convex, adaxial face concave, 1.4–1.7(–1.9) × 0.8–1 mm, apex obtuse, surfaces puncticulate.
dark brown to reddish brown, sessile, broadly ellipsoid, 1.8–2.1 × 0.8–1 mm, apex apiculate, surfaces glabrous to finely puncticulate.
Cyperus rotundus
Cyperus aggregatus
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 records of Cyperus aggregatus in New Jersey, Oregon, and Pennsylvania represent introductions from ballast.
The closely related Mexican and Central American Cyperus regiomontanus Britton has been collected once as an adventive or waif in southern California. It is distinguished from C. aggregatus by its silvery green, subulate-lanceolate spikelets and achenes that are only 0.4–0.6 mm wide.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
CA
LA Plants
MO Plants
WildflowerSearch
iNaturalist
USDA Plants Database
OR
Flora NW
PNW Herbaria
