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Red-root Flatsedge - Cyperus erythrorhizos
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.
Cyperus erythrorhizos is rare in Montana, where it is currently known from only three collections, one each from Dawson, Fergus, and Prairie Counties. Population levels and trends in the state are unknown. Surveys for the species may find additional occurrences in Montana. The species may be found in low elevation areas throughout Montana as the species is widespread though sporadically distributed across much of North America.
Surveys are needed at the previous collection sites to document the status of these populations. Information on the size and extent of the populations, habitat quality and potential threats need to be collected at these sites.
General Description
Caespitose annual. Stems ascending to erect, 10–70 cm. Leaves mainly basal, 2–9 mm wide, V- or W-shaped in cross-section. Inflorescence of hemispheric clusters of ovoid spikes of sessile spikelets. Spikelets cylindric, 3–10 mm long. Scales gold, apiculate, 1.5–2 mm long with 3 obscure, median veins. Flowers: stamens 3; style 3-branched. Achene elliptic, brown, 3-sided, 0.5–1 mm long, apiculate (
Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).
Phenology
Fruit mature in August.
Diagnostic Characteristics
Similar species include C. rivularis, C. acuminatus and C. aristatus, but all have globose rather than elongate spikes.
Species Range
Montana Range
Range Descriptions
Native
Range Comments
Throughout most of temperate U.S., Mexico. Known from Prairie County (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).
Observations in Montana Natural Heritage Program Database
Number of Observations: 3
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Relative Density
Recency
(Observations spanning multiple months or years are excluded from time charts)
Habitat
Reported elsewhere from valleys and lowlands, especially along the shores of major rivers.
National Vegetation Classification System Groups Associated with this Species
Wetland and Riparian
Riparian and Wetland Forest
Riparian Shrubland
Stewardship Responsibility
Threats or Limiting Factors
STATE THREAT SCORE REASON
Threat impact not assigned because threats are not known (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.
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