Juncus mertensianus
Mertens' rush
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Family: Juncaceae · Type: Grass · Native
Juncus mertensianus (Mertens' rush) is a native California grass in the Juncaceae family, recognized by flattened stems and high elevation alpine habitat.
Mertens' rush is a California native perennial rush found in the Klamath Ranges, northern California Coast Ranges, California Ranges, Sierra Nevada, Warner Mountains, and eastern Sierra Nevada in alpine and subalpine meadows, streambanks, and lake margins at elevations of 1,200 to 3,500 meters. With distinctive flat stems 15 to 45 centimeters tall, the plant produces clusters with more than 12 flowers featuring dark brown bractlets. Growing from a vertical, stout rhizome, it develops two to three cauline leaves with prominent sheath appendages and cylindric blades. Its leaves have complete crosswalls, with perianth parts measuring 3 to 4 millimeters long and appearing shiny brown-black. The fruit is oblong, approximately equal to or slightly shorter than the perianth, with a notched or truncate tip.
Identification and appearance
Key characters: 47 sympatric species; flattened stems and high elevation alpine habitat
Habitat and range
Habitat: Common. Alpine, subalpine meadows, streambanks, lake margins
Elevation: 1200-3500 m
California counties: Fresno, Mono, Siskiyou, Tulare, Amador, Madera, Nevada, Shasta, Tehama, Trinity, Tuolumne, Inyo, El Dorado, Modoc, Alpine, Los Angeles, Sierra, Plumas, Placer, Mariposa, Lassen, Butte, Marin, Humboldt, Del Norte
Outside California: to Alaska, Saskatchewan, New Mexico
How to tell it apart
vs Schoenoplectus: Juncus has leaf blades present; Schoenoplectus is leafless with only bladeless sheaths at base.; vs Carex: Juncus has round or flattened stems; Carex has triangular stems you can feel.; vs Luzula: Run finger along leaf edge - smooth = Juncus, hairy = Luzula.; vs Elegia: Juncus has small individual flowers; Elegia has showy papery bracts and branching structure.; vs Cyperus: Juncus has round stems and capsules; Cyperus has triangular stems and lens-shaped achenes.
Frequently asked questions
Is Juncus mertensianus native to California?
Yes. Juncus mertensianus is native to California (recorded as native).
Where in California does Juncus mertensianus grow?
Juncus mertensianus occurs in Fresno, Mono, Siskiyou, Tulare, Amador, Madera, Nevada, Shasta and other counties, at elevations of 1200-3500 m.
What plant family does Juncus mertensianus belong to?
Juncus mertensianus is in the Juncaceae family, genus Juncus.
What habitat does Juncus mertensianus grow in?
Juncus mertensianus grows in Common. Alpine, subalpine meadows, streambanks, lake margins.
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.