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Water Star-grass - Heteranthera dubia
State Rank Reason (see State Rank above)
Three occurrences known in Montana, two are moderate-sized populations and the third is of undocumented size. One population is adjacent to a campground and related human activity at this site may have extirpated the population. All sites are vulnerable to changes in hydrology, water quality and recreational impacts.
Water Star-grass is a submerged or partially floating, herbaceous perennial with long, flaccid stems that root at the nodes. The alternate, linear leaves are 7-15 cm long and have membranous wings at the base that clasp the stem. The solitary flowers are borne on stalks that elongate out of a tubular sheath, or spathe, that is borne in the upper leaf axils. Each small, yellow flower has 3 each of narrow, undifferentiated petals and sepals that are ca. 5 mm long and a long, slender basal tube that is 2-4 cm long and that appears to be a continuation of the stalk. Flowers float on the surface of the water. The fruit is a many-seeded capsule.
Flowering in August.
Species of Potamogeton have leaves with a distinct midrib, while leaves of H. dubia have veins but lack a distinct midvein.
BC to QC south to CA, MT, ID, MT, TX and VA. Collected in Flathead and Sanders counties (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)
Ecological Systems Associated with this Species
Threats or Limiting Factors
STATE THREAT SCORE REASON
Reported threats to Montana's populations of Water Star-grass are currently assigned as unknown. Potential threats due to motor boat recreation may have impacts at some locations, but the scope, severity, and timing of impacts are unknown (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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- Fassett, N. C. 1985. (3rd ed.) A Manual of Aquatic Plants, with Revision Appendix by E. C. Ogden. University of Wisconsin Press, Madison. 405 pp.
- Lesica, P., K. Lackschewitz, J. Pierce, S. Gregory and M. O'Brien. 1986. Noteworthy collections: Montana. Madrono 33:310-312.
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