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Blue Toadflax - Nuttallanthus texanus
Other Names:  Linaria canadensis var. texana

Species of Concern
Native Species

Global Rank: G4G5
State Rank: S1S2
(see State Rank Reason below)
State Threat Score: High - Medium

Agency Status


External Links

State Rank Reason (see State Rank above)
Known from one extant occurrence in southeastern Montana near Alzada and another occurrence from Makoshika State Park. Additional surveys and monitoring are needed.
  • Details on Status Ranking and Review
    Blue Toadflax (Nuttallanthus texanus) Conservation Status Review
    Review Date = 05/29/2013
    View State Conservation Rank Criteria
    Population Size

    Score2-3 - Very Small to Small: Population size is imprecisely known but is believed to be <10,000 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

    Score3 - Very Low: Generally occurring in 3 or fewer 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).


    Score2 - Moderate Declines: Species has experienced declines of 30-50% in population size, range extent and/or occupied area in the recent past (approximately 30 years).

    CommentPopulation trends are unknown, though habitat quality appears to have declined due to non-native species. Population levels probably fluctuate greatly from year to year.


    Score1-2 - Medium to High.

    CommentInvasive species have the potential to detrimentally impact this species and its habitat.

    Intrinsic Vulnerability

    Score1-2 - Moderate to High Vulnerability.

    Raw Conservation Status Score

    Score 12 to 15 total points scored out of a possible 19.

General Description
Blue Toadflax is a slender annual with erect, unbranched stems that are 1-5 dm tall. There is a rosette of prostrate stems at the base, the leaves of which are narrowly oblong, 5-10 mm long, and opposite or in whorls of 3. Stem leaves are narrower, and the lower are opposite or in whorls of 3, becoming alternate above. Foliage is glabrous, often with a thin, bluish, waxy coating. Short-stalked flowers are borne in an elongating, spike-like inflorescence. The snapdragon-like blue flowers are 8-12 mm long and have 5 sepals and a 2-lipped corolla. The lower lip is horizontal and 3-lobed, while the upper is 2-lobed and erect. There is a linear, downcurved spur that is 2-11 mm long and located at the base of the corolla. The fruit is a globose, many-seeded capsule that is 2-4 mm high.

Flowering in May-June.

Diagnostic Characteristics
The blue, spurred flowers and basal rosette of prostrate stems are diagnostic.

Species Range
Montana Range Range Descriptions


Range Comments
Midwest, Southeast and Pacific Coast from B.C. to Mexico. Peripheral.

Observations in Montana Natural Heritage Program Database
Number of Observations: 5

(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)

Open, sandy or acid shale soils of grasslands and woodlands on the plains. Habitat for occurrence near Alzada is described as pine-oak-juniper woodland on Mowry shale-clay with Cryptantha torreyana, Mentzelia dispersa, Mentzelia albicaulis and Vulpia octoflora.
Predicted Suitable Habitat Model

This species has a Predicted Suitable Habitat Model available.

To learn how these Models were created see

Blue toadflax is a winter annual (germinates in the fall) thus germination and seedling development are most affected by soil moisture availability in the fall.

Threats or Limiting Factors
Reported threats to Montana’s populations of Blue Toadflax are due to active bentonite mining in the vicinity of most (MTNHP Threat Assessment 2021). Moderate to serious negative impacts are expected to lead to population decline.

  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • 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.
    • Vanderhorst, J.P., S.V. Cooper, and B.L. Heidel. 1998. Botanical and vegetation survey of Carter County, Montana. Unpublished report prepared for the Bureau of Land Management. Montana Natural Heritage Program, Helena. 116 pp. + app.
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Citation for data on this website:
Blue Toadflax — Nuttallanthus texanus.  Montana Field Guide.  .  Retrieved on , from