E-Flora BC: Electronic Atlas of the Flora of British Columbia

Juncus mertensianus Bong.
Mertens' rush
Juncaceae (Rush family)

Introduction to Vascular Plants

© Bryan Kelly-McArthur  Email the photographer   (Photo ID #74333)

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Distribution of Juncus mertensianus
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Species Information

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Perennial herb from elongated rhizomes; stems arising singly, erect, 15-25 cm tall.
Located on the lower part of the stem, nearly circular in cross-section, tapered, the early leaves stiff, with prominent complete cross-walls; sheaths open, with rounded, ear-shaped lobes.
Numerous, in single, terminal, hemispheric heads; perianth segments dark brown, 3-4.5 mm long, pointed, the inner about the same length or shorter than the outer; stamens 6; anthers 0.6 mm long, shorter than the filaments; involucral bract solitary, short, equalling or exceeding the inflorescence.
Capsules, cylindrical to egg-shaped, rounded or with small depressions, slightly shorter than the perianth segments; seeds barrel-like, about 0.4 mm long, lacking tail-like appendages.

Source: The Illustrated Flora of British Columbia

USDA Species Characteristics

Flower Colour:
Blooming Period:
Late Spring
Fruit/Seed characteristics:
Colour: Brown
Present over the Summer
Source:  The USDA

Habitat / Range

Moist to wet meadows, pond edges, grassy streamsides, snowbed sites and open boggy forests from the montane to alpine zones; common throughout BC; amphiberingian, N to AK, YT and NT, E to AB and S to SD, NM, AZ and CA; Japan.

Source: The Illustrated Flora of British Columbia


Ecological Framework for Juncus mertensianus

The table below shows the species-specific information calculated from
original data (BEC database) provided by the BC Ministry of Forests and Range.
(Updated August, 2013)

Site Information
Value / Class




Elevation (metres) 100 1793 2468
Slope Gradient (%) 0 14 85
Aspect (degrees)
[0 - N; 90 - E; 180 - S; 270 - W]
0 180 360
Soil Moisture Regime (SMR)
[0 - very xeric; 4 - mesic;
8 - hydric]
0 5 8
Modal Nutrient Regime
Number of field plots
 species was recorded in:
Modal BEC Zone Class
All BEC Zones (# of stations/zone) species was recorded in: AT(20), BAFA(19), CMA(9), CWH(3), ESSF(123), ICH(3), IDF(1), IMA(7), MH(11), MS(1), SBS(2), SWB(4)


The climate type for this species, as reported in the: "British Columbia plant species codes and selected attributes. Version 6 Database" (Meidinger et al. 2008), is subalpine boreal & cool mesothermal.

Synonyms and Alternate Names

Juncus columbianus Coville
Juncus mertensianus subsp. mertensianus
Juncus mertensianus var. columbianus (Coville) F.J. Herm.
Juncus slwookoorum S.B. Young

Taxonomic and Nomenclatural Links

Additional Photo Sources

General References