Poa rhizomata
Timber blue grass, Timber Blue Grass
(c) Cheng-Tao Lin, some rights reserved (CC BY), uploaded by Cheng-Tao Lin · licence
Family: Poaceae · Type: Grass · Native
Conservation status: CNPS 1B.3
Poa rhizomata (Timber blue grass) is a native California grass in the Poaceae family, recognized by purple axillary buds and specialized habitat.
Timber blue grass is a rare (CNPS 1B.3) California native perennial found in the Klamath Ranges, specifically in northern Siskiyou and Trinity counties, on shady moist forest slopes at elevations of 400 to 1,000 meters. Flowering from April to July, this grass produces delicate pale green to bluish spikelets in loose, nodding clusters up to 10 centimeters long. Growing 25 to 60 centimeters tall with spreading rhizomes, it forms soft, flexible clumps in rich forest soils. Its leaves are soft and flat, 1.5 to 3.5 millimeters wide, with open sheaths and ligules 2 to 8 millimeters long. The spikelets feature hairy lemmas and cobwebby calluses, giving this grass a distinctive soft, wispy appearance.
Identification and appearance
Key characters: 24 sympatric species; distinguished by purple axillary buds and specialized habitat
Habitat and range
Habitat: Shady moist slopes in forest, in rich loose soils, on ultramafic substrates (but not serpentine)
Elevation: 400-1000 m
Outside California: to southwestern Oregon
Bloom period
Poa rhizomata blooms Apr-Jul.
Conservation status
CNPS 1B.3
How to tell it apart
vs Festuca: Poa has boat-shaped, keeled leaf tips; Festuca leaves are flat or rolled but never keeled like a ship's prow.; vs Melica: Poa has fine, narrow leaves with boat-shaped tips; Melica has wider, flat leaves without the distinctive keel.; vs Nassella: Poa leaves have boat-shaped tips you can feel; Nassella leaves roll inward and lack the keel.; vs Koeleria: Poa has cobwebby hairs at seed base and keeled leaf tips; Koeleria lacks both features.; vs Holcus: Poa has boat-shaped leaf tips; Holcus leaves are flat and soft-hairy without any keel.
Frequently asked questions
Is Poa rhizomata native to California?
Yes. Poa rhizomata is native to California (recorded as native).
When does Poa rhizomata bloom?
Poa rhizomata blooms Apr-Jul.
What plant family does Poa rhizomata belong to?
Poa rhizomata is in the Poaceae family, genus Poa.
Is Poa rhizomata rare or endangered?
Poa rhizomata carries California Rare Plant Rank 1B.3, state rank S2S3.
What habitat does Poa rhizomata grow in?
Poa rhizomata grows in Shady moist slopes in forest, in rich loose soils, on ultramafic substrates (but not serpentine).
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · CalPhotos · CDFW CNDDB
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.