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Slender Cottongrass - Eriophorum gracile
State Rank Reason (see State Rank above)
DRAFT: Requesting feedback on the 2026 revised rank, factors, and State Rank Reason outlined below and in the Conservation Status Rank Report.
Eriophorum gracile is a rare fen species of western Montana, being most common in the northwest portion of the state. Occurrences are almost entirely on publicly managed lands, including many on National Forest lands managed for multiple use and others on state-managed lands. A few occurrences are protected within Glacier National Park or Yellowstone National Park. Population levels appear to be relatively robust based on the available though limited data. Trends are unknown though populations have likely been relatively stable in the recent past or experienced only minor declines.
Climate change may negatively affect this species over the next several decades. However, the timing and magnitude of potential impacts are largely unknown. Although climate change is listed as a potential threat to the species, it does not affect the overall threat rank or scoring, or the final subnational rank.
Survey and monitoring data are needed to be able to more precisely determine population levels, assess condition and for assessing population trends.
General Description
Rhizomatous. Stems 25–60 cm. Leaves: V-shaped in cross-section; blades 1–2 mm wide. Inflorescence 25 ascending to nodding, pedunculate spikelets; bract 1, leaf-like, shorter than the inflorescence. Spikelets 15–35 mm long in fruit; lowest scale ca. as long as 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 et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).
Phenology
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 Descriptions
Native
Range Comments
Circumboreal south to CA, NV, UT, CO, IL and PA (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).
Observations in Montana Natural Heritage Program Database
Number of Observations: 68
(Click on the following maps and charts to see full sized version)
Relative Density
Recency
(Observations spanning multiple months or years are excluded from time charts)
Habitat
Wet, organic soil of fens from low to moderate elevations.
National Vegetation Classification System Groups Associated with this Species
Wetland and Riparian
Peatland
Stewardship Responsibility
Threats or Limiting Factors
STATE THREAT SCORE REASON
Reported threats to Montana's populations of Slender Cottongrass are currently assigned as unknown. Potential threats due to noxious species and development need to be substantiated before a threat rank can be assigned (MTNHP Threat Assessment 2021).
References
- Literature Cited AboveLegend:
View Online Publication- Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
MTNHP Threat Assessment. 2021. State Threat Score Assignment and Assessment of Reported Threats from 2006 to 2021 for State-listed Vascular Plants. Botany Program, Montana Natural Heritage Program, Helena, Montana.
- Additional ReferencesLegend: View Online Publication
Do you know of a citation we're missing?- Lesica, P., M.T. Lavin, and P.F. Stickney. 2022. Manual of Montana Vascular Plants, Second Edition. Fort Worth, TX: BRIT Press. viii + 779 p.
- Web Search Engines for Articles on "Slender Cottongrass"
