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Water Star-grass - Heteranthera dubia
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.
Heteranthera dubia is known from several waterbodies and waterways in northwest Montana. Aquatic surveys over the last ten years significantly increased the number of observations for the species, though it is still restricted in range and abundance. Most observations lack data on population levels, so a statewide population estimate cannot be made for the species. As a result, potential population trends also cannot be assessed. Widespread and significant threats are not known, though the species may be vulnerable to changes in water hydrology, decreases in water quality (increased nutrients and pollution), and recreational impacts such as increased motorboat use, which may have negative impacts at some locations. These potential threats, in conjunction with the species' limited range and unknown population numbers and trends make the species vulnerable within the state.
Data on population levels and monitoring are needed to estimate potential trends and to more accurately as
General Description
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.
Phenology
Flowering in August.
Diagnostic Characteristics
Species of Potamogeton have leaves with a distinct midrib, while leaves of H. dubia have veins but lack a distinct midvein.
Species Range
Montana Range
Range Descriptions
Native
Range Comments
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: 111
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
Relative Density
Recency
(Observations spanning multiple months or years are excluded from time charts)
Habitat
National Vegetation Classification System Groups Associated with this Species
Stewardship Responsibility
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).
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?- 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.
- 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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