Tapered Rush - Juncus acuminatus
State Rank Reason (see State Rank above)
Rare in Montana. Only known in the state from one wetland site in Teton County.
Short-rhizomatous, caespitose. Stems erect, terete, 40–80 cm, tufted. Leaves basal and cauline; blades subterete, 1–2 mm wide; auricles rounded. Inflorescence open with erect branches and clusters of 10 to 20+ flowers ca. 1 cm across; main bract shorter than the inflorescence. Flowers: prophylls absent; tepals green to light brown, 2–4 mm long, acuminate; stamens 3. Capsules 2–4 mm long, slightly exserted, tapering to the beak; seeds apiculate (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX)
Mature fruit in late July.
The septate leaves and flowers subtended by a single bract and having only 3 stamens separate J. acuminatus from our other non-rhizomatous rushes. Juncus is a large and difficult genus to distinguish, so a technical key should be consulted. Mature fruit is necessary for positive determination.
BC to NS south to most of U.S., Mexico, S. America, rare on the Great Plains. One collection from Teton County (Lesica 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).
Observations in Montana Natural Heritage Program Database
Number of Observations:
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(Observations spanning multiple months or years are excluded from time charts)
Wet soil on the margins of ponds and marshes in the valley zone and on the plains.
Ecological Systems Associated with this Species
- Additional ReferencesLegend: View Online Publication
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- Hermann, F.J. 1975. Manual of the rushes (Juncus spp.) of the Rocky Mountains and Colorado basin. U.S. Forest Service, General Technical Report RM-18.
- Lesica, P. 1991. The Rare Vascular Plants of Pine Butte Swamp Preserve. Unpublished Report to the Nature Conservancy. 15 Pp.
- Lesica, P., M. T. Lavin, and P. F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.