Search Field Guide
Advanced Search
MT Gov Logo
Montana Field Guide

Montana Field Guides

Diamond Clarkia - Clarkia rhomboidea

Species of Concern
Native Species

Global Rank: G5
State Rank: S3
(see State Rank Reason below)
State Threat Score: Low
CCVI: Less Vulnerable

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


External Links

State Rank Reason (see State Rank above)
Rare in Montana, where it is known from only a small portion of the northwest corner of the state, primarily along the lower Clark Fork River drainage. Some detrimental impacts from invasive weeds and subsequent herbicide treatments are possible as are loss of habitat due to fire suppression.
  • Details on Status Ranking and Review
    Diamond Clarkia (Clarkia rhomboidea) Conservation Status Review
    Review Date = 05/30/2013
    View State Conservation Rank Criteria
    Population Size

    Score1 - Moderate: Generally 10,000-100,000 individuals.

    Range Extent

    Score2 - Regional or State Endemic or Small Montana Range: Generally restricted to an area <100,000 sq. miles (equivalent to 2/3 the size of Montana or less) or Montana contributes 50% or more of the species’ range or populations OR limited to 2-3 Sub-basins in Montana.

    Area of Occupancy

    Score1 - Moderate: Generally occurring in 11-25 Subwatersheds (6th Code HUC’s).

    Environmental Specificity

    Score1 - Moderate: Species is restricted to a specific habitat that is more widely distributed or to several restricted habitats and is typically dependent upon relatively unaltered, good-quality habitat (C Values of 5-7).


    ScoreNA - Rank factor not assessed.

    CommentTrends unknown, though some habitat degradation has occurred.


    Score2 - High: 31-70% of the populations are being negatively impacted or are likely to be impacted by one or more activities or agents, which are expected to result in decreased populations and/or habitat quality and/or quantity.

    CommentInvasive weeds are common at some sites and have the potential to invade other locations. The severity of impacts is uncertain.

    Intrinsic Vulnerability

    Score1-2 - Moderate to High Vulnerability.

    Raw Conservation Status Score

    Score 8 to 9 total points scored out of a possible 16 (Rarity factors and threats only).

General Description
Common Clarkia is an annual with mostly unbranched stems that are 15-50 cm tall. The few leaves are opposite and have 1-3 cm long petioles and lance-shaped to elliptic, entire-margined, 2-7 cm long blades. The herbage is sparsely covered with short hairs. The few flowers are borne in a loose, narrow, nodding inflorescence which terminates the stem; the 4 separate petals are spoon-shaped, 5-10 mm long, and rose-purple, often with purple dots. The ovary is club-shaped and below the point of attachment of the petals. The fruits are capsules which are 1.5-3 cm long; each has a short beak at its tip.

Flowering in late May-June.

Diagnostic Characteristics
The species is most easily confused with Epilobium, but can be distinguished by having seeds without a tuft of hairs at the tip.

Species Range
Montana Range Range Descriptions


Range Comments
Collected in Lake, Lincoln, Ravalli, and Sanders counties in Montana. It occurs from WA to MT south to CA, AZ and UT (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Observations in Montana Natural Heritage Program Database
Number of Observations: 103

(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)

Dry, open forest slopes with gravelly soils in the montane 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
Reported threats to Montana's populations of Diamond Clarkia refer to noxious and other non-native plant populations and subsequent impacts from chemical herbicide used to control invasions (MTNHP Threat Assessment 2021). Dalmatian Toadflax (Linaria dalmatica), Spotted Knapweed (Centaurea stoebe) and Cheatgrass (Bromus tectorum) are found with many populations, and several of these reports describe heavy infestations.

  • 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?
    • 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.
    • Smith-Huerta, N.L. 1984. Seed germination in related diploid and allotetraploid Clarkia species. Botanical Gazette 145(2):246-252.
    • Vanderhorst, J.P. 1997. Status review of Clarkia rhomboidea in Montana. Unpublished report to the Kootenai National Forest. Montana Natural Heritage Program, Helena, MT 19 pp. plus appendices.
  • Web Search Engines for Articles on "Diamond Clarkia"
Login Logout
Citation for data on this website:
Diamond Clarkia — Clarkia rhomboidea.  Montana Field Guide.  .  Retrieved on , from