Scirpus cyperinus
Woolgrass
(c) Étienne Léveillé-Bourret, some rights reserved (CC BY) · licence
Family: Cyperaceae · Type: Grass · Not Native
Scirpus cyperinus (Woolgrass) is a non-native California grass in the Cyperaceae family, recognized by tall stature (1-2m) and prominent woolly bristles.
Woolgrass is a naturalized perennial found in central Sierra Nevada Highlands, specifically in Yosemite Valley and Mariposa County, growing on fresh moist streambanks and drying alluvial flats at approximately 1,200 meters elevation. Flowering from August to September, this plant produces red-brown to nearly black flowers in spikelets 3.5 to 8 millimeters long with pale green to brown midribs. Growing in dense tufts to 1 to 2 meters tall with cylindrical to triangular stems 3 to 5 millimeters in diameter, it forms a short rhizomatous base. Its leaves are relatively narrow, 3 to 10 millimeters wide, with ligules less than 1 millimeter wide, and distinctive curled perianth bristles that notably exceed the flower bracts. The small fruit is triangular, measuring 0.6 to 0.9 millimeters long.
Identification and appearance
Key characters: 2 sympatric species; key features are tall stature (1-2m) and prominent woolly bristles
Habitat and range
Habitat: Fresh moist streambanks, drying alluvial flats
Elevation: +- 1200 m.
Outside California: to Washington, eastern United States, southern Canada
Bloom period
Scirpus cyperinus blooms Aug-Sep.
How to tell it apart
vs Cyperus: Scirpus has drooping branched clusters, Cyperus has flat umbrella-like bracts radiating from a central point.; vs Schoenoplectus: Scirpus clusters are openly branched and spreading, Schoenoplectus has dense compact clusters.; vs Carex: Scirpus has perfect flowers in branched clusters, Carex has separate male/female spikes.; vs Bolboschoenus: Scirpus lacks underground tubers entirely, Bolboschoenus has firm tubers.; vs Juncus: Scirpus has obvious flowers in spikelets, Juncus has tiny flowers with visible petals/sepals.
Frequently asked questions
Is Scirpus cyperinus native to California?
No. Scirpus cyperinus is not native to California (recorded as not native).
When does Scirpus cyperinus bloom?
Scirpus cyperinus blooms Aug-Sep.
What plant family does Scirpus cyperinus belong to?
Scirpus cyperinus is in the Cyperaceae family, genus Scirpus.
What habitat does Scirpus cyperinus grow in?
Scirpus cyperinus grows in Fresh moist streambanks, drying alluvial flats.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · 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.