Agrostis idahoensis
Idaho redtop, Idaho Redtop
Hitchcock, A.S. (rev. A. Chase). 1950. Manual of the grasses of the United States. USDA Misc. Publ. No. 200. Washington, DC. 1950. (via Wikimedia Commons) · CC0
Family: Poaceae · Type: Grass · Native
Agrostis idahoensis (Idaho redtop) is a native California grass in the Poaceae family, recognized by small stature, narrow inrolling leaves, awnless lemmas, and very short anthers.
Idaho redtop is a California native perennial found in northwestern California, the Cascade Range, Sierra Nevada, northern San Francisco Bay Area, San Bernardino Mountains, San Jacinto Mountains, and White and Inyo Mountains in open, wet meadows and conifer forests at elevations up to 3,500 meters. Flowering from July to August, this plant produces delicate, pale grass-like flowers in loose, lanceolate panicles 3 to 13 centimeters long. Growing with slender stems 8 to 30 centimeters tall, it forms clumps with both basal and stem leaves. Its leaves are narrow, often 1 to 5 centimeters long and 0.5 to 2 millimeters wide, typically flat but becoming slightly inrolled as they mature. The grass has tiny, pale spikelets with glumes 1.5 to 2.5 millimeters long and lemmas without awns.
Identification and appearance
Key characters: 16 sympatric species; key features are small stature, narrow inrolling leaves, awnless lemmas, and very short anthers
Habitat and range
Habitat: Open, wet meadows, conifer forest
Elevation: < 3500 m
California counties: Los Angeles, Alpine, Amador, Butte, El Dorado, Fresno, Humboldt, Inyo, Kern, Lassen, Mariposa, Mono, Nevada, Placer, Riverside, San Bernardino, Siskiyou, Tehama, Tulare, Tuolumne, Calaveras, Madera, Yuba, Trinity, Shasta, Plumas, Sierra, Modoc, Mendocino
Outside California: to British Columbia, western United States
Bloom period
Agrostis idahoensis blooms Jul-Aug.
How to tell it apart
vs Oloptum: Oloptum has prominent bent awns; Agrostis awns are tiny or absent.; vs Holcus: Holcus has velvety-hairy spikelets; Agrostis spikelets are smooth and glossy.; vs Polypogon: Polypogon has dense bristly panicles; Agrostis panicles are airy and delicate.; vs Poa: Poa has boat-shaped lemmas with 5 veins; Agrostis lemmas are rounded with faint veins.; vs Festuca: Festuca has multiple flowers per spikelet; Agrostis has single-flowered spikelets.
Frequently asked questions
Is Agrostis idahoensis native to California?
Yes. Agrostis idahoensis is native to California (recorded as native).
When does Agrostis idahoensis bloom?
Agrostis idahoensis blooms Jul-Aug.
Where in California does Agrostis idahoensis grow?
Agrostis idahoensis occurs in Los Angeles, Alpine, Amador, Butte, El Dorado, Fresno, Humboldt, Inyo and other counties, at elevations of < 3500 m.
What plant family does Agrostis idahoensis belong to?
Agrostis idahoensis is in the Poaceae family, genus Agrostis.
What habitat does Agrostis idahoensis grow in?
Agrostis idahoensis grows in Open, wet meadows, conifer forest.
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.