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Montana Field Guide

Montana Field Guides

Water Star-grass - Heteranthera dubia

Species of Concern
Native Species

Global Rank: G5
State Rank: S1S2
(see State Rank Reason below)
State Threat Score: Unknown
C-value: 7

Agency Status
USFS: Sensitive - Known in Forests (KOOT)


External Links

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.
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.

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


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: 106

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)

Shallow water of riverine sloughs, backwaters; valleys (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).
Predicted Suitable Habitat Model

This species has a Predicted Suitable Habitat Model available.

To learn how these Models were created see

Ecological Systems Associated with this Species
  • Commonly Associated with these Ecological Systems
    Wetland and Riparian Systems

Threats or Limiting Factors
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
    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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Citation for data on this website:
Water Star-grass — Heteranthera dubia.  Montana Field Guide.  .  Retrieved on , from