Isoetes occidentalis
Western quillwort
(c) Dean Wm. Taylor, some rights reserved (CC BY) · licence
Family: Isoetaceae · Type: Grass · Native
Isoetes occidentalis (Western quillwort) is a native California grass in the Isoetaceae family, recognized by habitat (persistent water), high elevation, dark green brittle evergreen leaves.
Western quillwort is a California native aquatic perennial found in the Klamath Ranges and Sierra Nevada Highlands in persistent lakes and high-elevation pools above 1,500 meters. This distinctive underwater plant produces no visible flowers, instead reproducing through specialized spores with unique characteristics. Growing with evergreen leaves less than 20 centimeters long, the plant features rigid, brittle, dark green leaves that taper to a point and have a distinctive brown-white base. Its leaves emerge completely underwater, with a remarkable structural complexity including male spores around 0.035 to 0.045 millimeters and larger female spores approximately 0.5 to 0.7 millimeters with intricate ridged and tubercled surfaces. The plant's genetic makeup is notably complex, with a chromosome count of 2n=66, reflecting its sophisticated evolutionary adaptation to persistent aquatic environments.
Identification and appearance
Key characters: 5 sympatric species - key features are habitat (persistent water), high elevation, dark green brittle evergreen leaves
Habitat and range
Habitat: Persistent lakes, pools
Elevation: > 1500 m
California counties: Sierra, Tuolumne, Siskiyou, Tulare, El Dorado, Fresno, Inyo, Nevada, Madera, Amador, Trinity, Plumas, Mariposa, Mono
Outside California: to British Columbia, Colorado
How to tell it apart
vs Juncus: Isoetes has a bulbous corm-like base with embedded spore capsules; Juncus has fibrous roots without sporangia.; vs Subularia: Isoetes leaves arise from a bulbous base; Subularia has a thin taproot with small white flowers above the leaves.; vs Triglochin: Isoetes has spore capsules at leaf bases; Triglochin produces tall flower spikes with tiny greenish flowers.; vs Sparganium: Isoetes forms tight tufts from a corm; Sparganium has creeping stems and round, burr-like flower heads.; vs Pilularia: Isoetes leaves stand rigidly erect; Pilularia leaves coil in fiddlehead fashion when young.
Frequently asked questions
Is Isoetes occidentalis native to California?
Yes. Isoetes occidentalis is native to California (recorded as native).
Where in California does Isoetes occidentalis grow?
Isoetes occidentalis occurs in Sierra, Tuolumne, Siskiyou, Tulare, El Dorado, Fresno, Inyo, Nevada and other counties, at elevations of > 1500 m.
What plant family does Isoetes occidentalis belong to?
Isoetes occidentalis is in the Isoetaceae family, genus Isoetes.
What habitat does Isoetes occidentalis grow in?
Isoetes occidentalis grows in Persistent lakes, pools.
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.