Setaria parviflora
Knotroot bristle grass, Knotroot Bristle Grass
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Family: Poaceae · Type: Grass · Native
Setaria parviflora (Knotroot bristle grass) is a native California grass in the Poaceae family, recognized by only native, only perennial, diagnostic knotty stem base.
Knotroot bristle grass is a native perennial found in northern Sierra Nevada Foothills, Great Valley, central western California, southern Desert Mountains, and southwestern California in moist, disturbed areas, roadsides, and streambanks at elevations below 1,470 meters. Flowering from May to September, this grass produces small pale greenish-white spikelets in dense clusters 3 to 8 centimeters long. Growing with robust stems 70 to 120 centimeters tall, the plant has distinctive hard, knot-like swellings at its base that create a characteristic clumped growth pattern. Its leaves are narrow, 2 to 8 millimeters wide and up to 25 centimeters long, with smooth upper surfaces and relatively short leaf sheaths. The plant's unique spikelets feature 4 to 12 bristles and measure approximately 2 to 3 millimeters in length, with delicate lower and upper glumes.
Identification and appearance
Key characters: 6 sympatric species; only native, only perennial, diagnostic knotty stem base
Habitat and range
Habitat: Moist, disturbed areas, roadsides, streambanks, canal banks
Elevation: < 1470 m
California counties: San Diego, Stanislaus, Ventura, Los Angeles, San Bernardino, Merced, Alameda, Kern, San Luis Obispo, Fresno, Sacramento, Orange, Santa Barbara, Butte, Riverside, Marin, Tulare, Calaveras, Sonoma, Placer, Contra Costa, Glenn, Mariposa, Monterey, Nevada, San Francisco, San Mateo, Santa Cruz, Yuba, El Dorado, Humboldt, Santa Clara, Sutter, Madera, Colusa, Mono, Yolo, Tehama, Solano, Imperial, San Joaquin, Kings
Outside California: to eastern United States, Central America, South America
Bloom period
Setaria parviflora blooms May-Sep.
How to tell it apart
vs Cenchrus: Setaria bristles stay attached to the axis after the spikelet falls; Cenchrus bristles fuse into a spiny bur that drops with the seed.; vs Pennisetum: Setaria bristles are free and persistent below each spikelet; Pennisetum bristles form a deciduous involucre that falls as a unit with the spikelet.; vs Alopecurus: Setaria has stiff bare bristles subtending naked spikelets; Alopecurus has no bristles and its soft spikelets bear a bent awn from the lemma back.; vs Polypogon: Setaria's bristles are separate sterile branchlets left behind on the axis; in Polypogon the bristly look comes from awns on the glumes and the whole spikelet sheds.; vs Phleum: Setaria's cylindric head has projecting bristles between the spikelets; Phleum's dense spike is bristle-free with stiff, short-awned, keeled glumes.
Frequently asked questions
Is Setaria parviflora native to California?
Yes. Setaria parviflora is native to California (recorded as native).
When does Setaria parviflora bloom?
Setaria parviflora blooms May-Sep.
Where in California does Setaria parviflora grow?
Setaria parviflora occurs in San Diego, Stanislaus, Ventura, Los Angeles, San Bernardino, Merced, Alameda, Kern and other counties, at elevations of < 1470 m.
What plant family does Setaria parviflora belong to?
Setaria parviflora is in the Poaceae family, genus Setaria.
What habitat does Setaria parviflora grow in?
Setaria parviflora grows in Moist, disturbed areas, roadsides, streambanks, canal banks.
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.