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Montana Field Guide

Montana Field Guides

Slender Cottongrass - Eriophorum gracile

Species of Concern
Native Species

Global Rank: G5
State Rank: S3
(see State Rank Reason below)

Agency Status
MNPS Threat Rank: 2
C-value: 10

External Links

State Rank Reason (see State Rank above)
Known from a very few large populations, several smaller populations and a half dozen historical or poorly documented locations. Populations occur on a mix of federal, state and private ownerships in northwest Montana at low to moderate elevations. Populations are vulnerable to any activities that may alter the hydrology of occupied sites.
General Description
Rhizomatous. Stems 15–60 cm. Leaves: upper leaf blades rudimentary; lower blades V-shaped or trinagular in cross-section, 1–2 mm wide. Inflorescence a solitary, erect spikelet; bracts absent. Spikelets 15–35 mm long in fruit; lowest scale lanceolate, shorter than the spikelet. Fertile scales brown to black with pale margins, 4–7 mm long. Bristles becoming tawny-brown. Achene 2–3 mm long, apiculate (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Flowering in late June - early July.

Diagnostic Characteristics
Eriophorum viridicarinatum and the more common E. polystachyon have two or more leaf-like bracts subtending the inflorescence, at least one of which is longer than the spikelets. Both of these species also have black seeds and leaves that are flat for most of their length.

Species Range
Montana Range


Range Comments
Circumboreal south to CA, NV, UT, CO, IL and PA (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Observations in Montana Natural Heritage Program Database
Number of Observations: 60

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)

Wet, organic soil of fens from low to moderate elevations.
Predicted Suitable Habitat Model

This species has a Predicted Suitable Habitat Model available.

To learn how these Models were created see

Ecological Systems Associated with this Species

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Citation for data on this website:
Slender Cottongrass — Eriophorum gracile.  Montana Field Guide.  .  Retrieved on , from