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Montana Field Guide

Montana Field Guides

Island Koenigia - Koenigia islandica

Species of Concern
Native Species

Global Rank: G4
State Rank: S2
(see State Rank Reason below)
State Threat Score: No Known Threats
CCVI: Extremely Vulnerable
C-value: 10

Agency Status


External Links

State Rank Reason (see State Rank above)
Rare in Montana, where it is only known from several, high elevation sites on the Beartooth Plateau. Data are insufficient for accurately determining population levels and trend, though populations probably flucuate widely from year to year. The known occurrences and their habitat do not appear to be at any significant risk of adverse impacts from human activities.
General Description
Island Koenigia is a small, glabrous annual with simple or sparsely branched, ascending to nearly prostrate stems that are 1-4 cm high. The narrowly elliptic, entire-margined, opposite or alternate leaves are fleshy, reddish-tinged, and 2-5 mm long. Small plants may have only a single pair of leaves. Tiny flowers occur in small clusters on top of the stems or in the axils of the upper leaves. Each flower has 3 greenish calyx lobes and 3 stamens. Petals are lacking. The fruit is a tiny 3-angled achene.

Flowering in August.

Diagnostic Characteristics
Small, alpine species of Polygonum have 4-5 tepals. Small specimens of Epilobium alpinum may be mistaken for K. islandica, but the former has leaves with a more prominent midvein, and the flowers have a linear ovary.

Species Range
Montana Range Range Descriptions


Range Comments
Circumpolar, extending south in North America to scattered alpine summits in the Rocky Mountains as far south as Colorado.

Observations in Montana Natural Heritage Program Database
Number of Observations: 20

(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)

Wet, open, gravelly soil in seepage areas in the alpine zone.
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

Threats or Limiting Factors
Threat impact not assigned because threats are not known (MTNHP Threat Assessment 2021).

  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Fertig, W. and M. Bynum. 1994. Biological report on the proposed Twin Lakes Research Natural Area. Unpublished report to the Shoshone National Forest. Wyoming Natural Diversity Database, Laramie, Wyoming. 33 pp. plus appendices.
    • Lesica, P. 1993. Vegetation and flora of the Line Creek Plateau area, Carbon County, Montana. Unpublished report to USDA Forest Service, Intermountain Research Station. Montana Natural Heritage Program, Helena, Montana. 30 pp.
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
    • 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:
Island Koenigia — Koenigia islandica.  Montana Field Guide.  .  Retrieved on , from