Cascade reedgrass - Calamagrostis tweedyi
State Rank Reason (see State Rank above)
A species of limited distribution and currently considered to be globally rare. Restricted in Montana to the extreme western portion of the state.
Cascade Reedgrass is a glabrous perennial arising from a short rhizome with flowering stems which stand 4-15 dm tall. The blades of the stem leaves are flat, 5-13 mm wide, and up to about 12 cm long; leaves from short vegetative shoots have somewhat narrower and longer blades (up to 30 cm). The leaves have open sheaths and membranous ligules, which are 6-15 mm long, but no auricles. Numerous spikelets are borne in a compact panicle which is 8-16 cm long and about 2 cm wide. The spikelets consist of 2 glumes which enclose a single floret. The glumes are approximately equal in size, 4.5-9 mm long, and slightly longer than the lemma. A sharply bent awn arises from around the middle of the lemma back and exceeds the glumes by about 5 mm. The callus is slightly bearded with hairs less than 1 mm long.
Fruiting in July.
Distinguished from other Calamagrosis in Montana by the combination of having flat leaves, a long bent awn, and an only slightly bearded callus. Vegetative plants of the species may be identified by the leaf and habit characters given above, but closely resemble Cinna latifolia, which grows along with the species in Montana.
Collected in Mineral and Ravalli counties; WA, ID and MT (Lavin in Lesica et al. 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)
Seral stages of Douglas-fir and subalpine fir forests in the montane zone.
Ecological Systems Associated with this Species
Threats or Limiting Factors
STATE THREAT SCORE REASON
Threat impact not assigned because threats are not known (MTNHP Threat Assessment 2021).
- 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.
- Additional ReferencesLegend: View Online Publication
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- 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.