Poa thomasii
California dissanthelium
(c) Sula Vanderplank, some rights reserved (CC BY) · licence
Family: Poaceae · Type: Grass · Native
Conservation status: CNPS 1B.2
Poa thomasii (California dissanthelium) is a native California grass in the Poaceae family, recognized by but unique to southern Channel Islands habitat.
California dissanthelium is a rare (CNPS 1B.2) California native annual grass found on the southern Channel Islands, specifically Santa Catalina and San Clemente islands, in coastal sage scrub at elevations below 100 meters. Flowering from March to May, this delicate grass produces small, subtle flowers in loosely contracted inflorescences with slender, scabrous branches. Growing in slender tufts up to 25 centimeters tall, it forms sometimes solitary clusters with soft, flat leaf blades 2.5 to 15 centimeters long and 1 to 4 millimeters wide. Its leaves have open sheaths and slender green blades, with spikelets featuring thin glumes that exceed the lower florets and are slightly hairy. The uppermost florets within the spikelets may be pistillate, with tiny anthers less than 1 millimeter long.
Identification and appearance
Key characters: 18 sympatric species but unique to southern Channel Islands habitat
Habitat and range
Habitat: Coastal sage scrub
Elevation: < 100 m
Outside California: Baja California (Guadalupe Island)
Bloom period
Poa thomasii blooms Mar-May.
Conservation status
CNPS 1B.2
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 thomasii native to California?
Yes. Poa thomasii is native to California (recorded as native).
When does Poa thomasii bloom?
Poa thomasii blooms Mar-May.
What plant family does Poa thomasii belong to?
Poa thomasii is in the Poaceae family, genus Poa.
Is Poa thomasii rare or endangered?
Poa thomasii carries California Rare Plant Rank 1B.2, state rank S1.
What habitat does Poa thomasii grow in?
Poa thomasii grows in Coastal sage scrub.
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.