Page author: Don Knoke
Cyperus erythrorhizos
redroot flatsedge
WTU specimens
Other herbaria

Distribution: Widespresd in the United Stated and adjacent Canada.

Habitat: Streambanks and other wet places in the valleys and lowlands.

Flowers: June - August

Origin: Native

Conservation Status: Not of concern


Tufted annual, the triangular, solid, stout stems 1-7 dm. tall.


Leaves grass-like, crowded near the base, the elongate blade 2-9 mm. wide, the sheaths closed.


Inflorescence of clustered, cylindrical spikes, the terminal cluster sessile, the others on rays up to 7 cm. long, each spike 1-4 cm. long, with numerous, spirally arranged spikelets on an elongate rachis; scales of the spikelets in two vertical rows, 1.2-1.5 mm. long, with a green keel, closely set; perianth none; stamens 3; style trifid.


Achenes unequally triangular, 0.7-1.0 mm. long, pale and shining.

Accepted Name:
Cyperus erythrorhizos Muhl.
Publication: Descr. Gram. 20. 1817. 1817.

Synonyms & Misapplications:
Cyperus cupreus J. Presl & C. Presl
Cyperus erythrorhizos Muhl. var. cupreus (J. Presl & C. Presl) Kük.
Cyperus halei Torr. ex Britton
Cyperus occidentalis Torr.
Cyperus washingtonensis Gand.
Additional Resources:

PNW Herbaria: Specimen records of Cyperus erythrorhizos in the Consortium of Pacific Northwest Herbaria database.

WA Flora Checklist: Cyperus erythrorhizos checklist entry.

E-Flora BC: Cyperus erythrorhizos atlas page.

CalPhotos: Cyperus erythrorhizos photos.

USDA Plants: Cyperus erythrorhizos information.

15 photographs:
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