Cyperus

Illustrator: Yevonn Wilson-Ramsey

Copyright: Flora of North America Association

Herbs, perennial or less often annual, cespitose or not, rhizomatous, stoloniferous, rarely tuberous. Culms solitary or not, trigonous or round, glabrous or scabridulous with extrorse or antrorse (rarely retrorse) prickles. Leaves usually basal; ligules absent; blades keeled abaxially, flat, V-, or inversely W-shaped in cross section. Inflorescences terminal, rarely pseudolateral, 1st order subumbellate to capitate, 2d order with spicate or digitately arranged spikelets, rarely a solitary spikelet; spikelets 1–150; 1st order rays unequal (rarely equal) in length, produced singly from the axils of inflorescence bracts; involucral bracts 1–22, spirally arranged at culm apex, spreading to erect, leaflike. Spikelets: scales to 76, distichous, each subtending flower, cylindric to compressed, borne spicately or digitately at ends of rays (occasionally proliferous). Flowers bisexual [rarely unisexual], in axils of distichous floral scales, bases often decurrent onto rachilla as ± hyaline wings; perianth absent; stamens 1–3; styles linear, 2–3-fid, base deciduous or persistent; stigmas 2–3. Achenes biconvex, flattened, or trigonous.

Distribution

Pantemperate and tropical.

Discussion

Species ca. 600 (96 in the flora).

Selected References

Carter, J. R. 1984. A Systematic Study of the New World Species of Section Umbellati of Cyperus. Ph.D. dissertation. Vanderbilt University.

Corcoran, M. L. 1941. A revision of the subgenus Pycreus in North and South America. Catholic Univ. Amer., Biol. Ser. 37: 1–68.

Denton, M. F. 1978b. The Luzulae group of Cyperus (Cyperaceae). Contr. Univ. Michigan Herb. 11: 197–271.

Horvat, M. L. 1941. A revision of the subgenus Mariscus found in the United States. Catholic Univ. Amer., Biol. Ser. 33: 1–147.

Marcks, B. G. 1972. Population Studies of North American Cyperus Section Laxiglumi (Cyperaceae). Ph.D. dissertation. University of Wisconsin.

Marcks, B. G. 1974. Preliminary reports on the flora of Wisconsin, no. 66. Cyperaceae II—Sedge family II. The genus Cyperus—the umbrella sedges. Trans. Wisconsin Acad. Sci. 62: 261–284.

McGivney, M. V. 1938. A revision of the subgenus Eucyperus found in the United States. Catholic Univ. Amer., Biol. Ser. 26: 1–74.

Tucker, G. C. 1983. The taxonomy of Cyperus (Cyperaceae) in Costa Rica and Panama. Syst. Bot. Mongr. 2: 1–85.

Tucker, G. C. and R. McVaugh. 1993. Cyperus. In: R. McVaugh and W. R. Anderson, eds. 1974+. Flora Novo-Galiciana: A Descriptive Account of the Vascular Plants of Western Mexico. 8+ vols. Ann Arbor. Vol. 3, pp. 270–344.

Tucker, G. C. 1994. A revision of the Mexican species of Cyperus L. (Cyperaceae). Syst. Bot. Monogr. 43: 1–214.

Lower Taxa

Cyperus subg. Cyperus, Cyperus subg. Diclidium, Cyperus subg. Juncellus, Cyperus subg. Pycnostachys, Cyperus subg. Pycreus

Key

1	Stigmas 2 (3 in C. serotinus); achenes biconvex.	> 2
1	Stigmas 3; achenes trigonous, plano-convex, or terete.	> 3
2	Achenes laterally flattened, borne with edge toward rachilla.	Cyperus subg. Pycreus
2	Achenes dorsiventrally flattened, borne with face toward rachilla.	Cyperus subg. Juncellus
3	Spikelets borne in digitate clusters (rarely singly) or in umbellate or glomerulate heads.	Cyperus subg. Pycnostachys
3	Spikelets borne in spikes on conspicuous rachis.	> 4
4	Rachilla continuous or articulate only at base.	Cyperus subg. Cyperus
4	Rachilla articulate at base of each scale, mature spikelet disarticulating into segments consisting of scale, internode, and rachilla wings.	Cyperus subg. Diclidium