Cyperus difformis
Variable flatsedge
no rights reserved, uploaded by 葉子 · CC0
Family: Cyperaceae · Type: Grass · Not Native
Cyperus difformis (Variable flatsedge) is a non-native California grass in the Cyperaceae family, recognized by dense spherical heads with 50+ spikelets diagnostic.
Variable flatsedge is a naturalized annual found in the Great Valley and southwestern California in ditches, pond shores, and rice fields at elevations of 100 to 500 meters. Flowering from July to November, this plant produces yellow to yellow-brown flowers in dense, nearly spherical heads with 50 to 100 small spikelets. Growing 3 to 40 centimeters tall with slender stems, it forms compact inflorescences with 2 to 3 bracts and up to 4 spreading rays. Its flower bracts are small, about 0.6 to 0.8 millimeters long, and obovate in shape with three distinctive stigmas. The tiny fruits are glossy, obovoid-ellipsoid, and measure 0.6 to 0.8 millimeters long.
Identification and appearance
Key characters: 18 sympatric species; dense spherical heads with 50+ spikelets diagnostic
Habitat and range
Habitat: Ditches, pond shores, rice fields
Elevation: 100-500 m
California counties: Glenn, Riverside, Tehama, San Diego, Butte, San Bernardino, Colusa, Fresno, Kern, Los Angeles, Madera, Merced, Orange, Santa Barbara, Santa Clara, Stanislaus, Sutter, Yolo, Imperial, Sacramento, Plumas, Sonoma, Alameda, Marin, San Francisco, Napa, Tulare, Kings, Contra Costa, Yuba, Nevada, Santa Cruz, San Luis Obispo, Tuolumne, San Joaquin
Outside California: to Oregon, Utah, eastern North America, native to Old World
Bloom period
Cyperus difformis blooms Jul-Nov.
How to tell it apart
vs Carex: Cyperus has umbrella clusters with flat spikes; Carex has brown/green spikelets with seeds in individual flasks.; vs Scirpus: Cyperus has flattened ribbon-like spikes; Scirpus has rounded, cylindrical spikelets.; vs Juncus: Cyperus has triangular stems and flat flower spikes; Juncus has round stems and individual flowers.; vs Sticherus: Cyperus is a sedge with triangular stem; Sticherus is a fern with fronds.; vs Eleusine: Cyperus has triangular stems; Eleusine is a grass with round stems and obvious grass flowers.
Frequently asked questions
Is Cyperus difformis native to California?
No. Cyperus difformis is not native to California (recorded as not native).
When does Cyperus difformis bloom?
Cyperus difformis blooms Jul-Nov.
Where in California does Cyperus difformis grow?
Cyperus difformis occurs in Glenn, Riverside, Tehama, San Diego, Butte, San Bernardino, Colusa, Fresno and other counties, at elevations of 100-500 m.
What plant family does Cyperus difformis belong to?
Cyperus difformis is in the Cyperaceae family, genus Cyperus.
What habitat does Cyperus difformis grow in?
Cyperus difformis grows in Ditches, pond shores, rice fields.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · Index of California Plant Names · CalPhotos
Last updated 2026-10-07
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.