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Montana Field Guides

Annual Indian Paintbrush - Castilleja exilis
Other Names:  Castilleja minor ssp. minor, Castilleja minor

Species of Concern
Native Species

Global Rank: G5T5
State Rank: S2
(see State Rank Reason below)
State Threat Score: Low
CCVI: Extremely Vulnerable
C-value: 6

Agency Status
USFS: Species of Conservation Concern in Forests (CG)


External Links

State Rank Reason (see State Rank above)
Annual Indian Paintbrush is known from a half dozen counties in southwest Montana with the majority of documented locations on private lands. Many areas of suitable habitat have been converted to agricultural uses and/or are used for livestock grazing. Additionally, populations are susceptible to hydrologic changes and may be negatively impacted by invasive weeds.
General Description
Annual Indian Paintbrush is an annual with erect, unbranched stems that are 3-8 dm high. The alternate, narrowly lance-shaped leaves, 3-8 cm long, have entire margins. Foliage is glandular-hairy. The stalkless flowers arise from the axils of the reduced upper leaves (bracts) in a spike-like inflorescence at the top of the stem. The upper bracts have red tips. The yellowish, tubular corolla, 15-25 mm long, tapers to a galea above that surpasses the 3 small lobes below. The tubular calyx, 15-20 mm long, almost completely contains the corolla and is cleft into 4 pointed lobes. The fruit is a capsule with many tiny seeds.

Flowering in July-August.

Diagnostic Characteristics
This is our only annual Castilleja, also distinguished in the lack of lobes on the leaves and bracts. It can be distinguished from annual Orthocarpus and Cordylanthus by the galea that is appreciably longer than the lower corolla lip.

Species Range
Montana Range Range Descriptions


Range Comments
WA to MT south to CA, AZ and NM (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Observations in Montana Natural Heritage Program Database
Number of Observations: 54

(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)

Moist alkaline meadows in the valley 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

The following animal species have been reported as pollinators of this plant species or its genus where their geographic ranges overlap: Bombus appositus, Bombus bifarius, Bombus fervidus, Bombus flavifrons, Bombus melanopygus, Bombus sylvicola, Bombus occidentalis, and Bombus kirbiellus (Macior 1974, Thorp et al. 1983, Bauer 1983, Mayer et al. 2000, Wilson et al. 2010, Pyke et al. 2012, Koch et al. 2012, Miller-Struttmann and Galen 2014, Williams et al. 2014).

Threats or Limiting Factors
Reported threats to Montana's populations of Annual Indian Paintbrush include populations exposed to hydrologic alteration, non-native plant encroachment, livestock trampling and recreation (MTNHP Threat Assessment 2021). Most populations are known on private lands and extensive potential habitat has been converted to agricultural use. Ditching and diversion is commonly employed on agricultural lands and can inadvertently impact neighboring Annual Paintbrush populations. Leafy Spurge (Euphorbia virgata) and other exotic species are reported to occur among or in the vicinity of several populations. Moderate disturbance from livestock trampling is likely beneficial to Annual Indian Paintbrush, but reports of severe trampling at several populations are a concern.

  • Literature Cited AboveLegend:   View Online Publication
    • Bauer, P.J. 1983. Bumblebee pollination relationships on the Beartooth Plateau tundra of Southern Montana. American Journal of Botany. 70(1): 134-144.
    • Koch, J., J. Strange, and P. Williams. 2012. Bumble bees of the western United States. Washington, DC: USDA Forest Service, Pollinator Partnership. 143 p.
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
    • Macior, L.M. 1974. Pollination ecology of the Front Range of the Colorado Rocky Mountains. Melanderia 15: 1-59.
    • Mayer, D.F., E.R. Miliczky, B.F. Finnigan, and C.A. Johnson. 2000. The bee fauna (Hymenoptera: Apoidea) of southeastern Washington. Journal of the Entomological Society of British Columbia 97: 25-31.
    • Miller-Struttmann, N.E. and C. Galen. 2014. High-altitude multi-taskers: bumble bee food plant use broadens along an altitudinal productivity gradient. Oecologia 176:1033-1045.
    • Pyke, G.H., D.W. Inouye, and J.D. Thomson. 2012. Local geographic distributions of bumble bees near Crested Butte, Colorado: competition and community structure revisited. Environmental Entomology 41(6): 1332-1349.
    • Thorp, R.W., D.S. Horning, and L.L. Dunning. 1983. Bumble bees and cuckoo bumble bees of California (Hymenoptera: Apidae). Bulletin of the California Insect Survey 23:1-79.
    • Williams, P., R. Thorp, L. Richardson, and S. Colla. 2014. Bumble Bees of North America. Princeton, NJ: Princeton University Press. 208 p.
    • Wilson, J.S., L.E. Wilson, L.D. Loftis, and T. Griswold. 2010. The montane bee fauna of north central Washington, USA, with floral associations. Western North American Naturalist 70(2): 198-207.
  • 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.
  • Web Search Engines for Articles on "Annual Indian Paintbrush"
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Citation for data on this website:
Annual Indian Paintbrush — Castilleja exilis.  Montana Field Guide.  .  Retrieved on , from