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Montana Field Guide

Montana Field Guides

Western Trillium - Trillium ovatum

Native Species

Global Rank: G5
State Rank: S4S5
C-value: 6

Agency Status


External Links

General Description
Short-rhizomatous, fibrous-rooted, glabrous perennials. Stems erect, 10–40 cm, naked below. Leaves (bracts) 3, sessile, whorled at the stem tip, 3–13 cm long, broadly ovate, acuminate. Inflorescence a solitary, terminal flower; pedicel 15–60 mm long. Flower regular, star-shaped; sepals green, narrowly lanceolate, 15–35 mm long; petals white or pinkish, fading to pink or reddish, separate, 25–40 mm; stamens shorter than petals; anthers yellow; style 3-lobed. Fruit a broadly ovoid, 3-winged, many-seeded capsule, 12–25 mm long (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX; Hichcock and Cronquist 1973)

Species Range
Montana Range Range Descriptions


Range Comments
AB south to CA, ID and CO (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Observations in Montana Natural Heritage Program Database
Number of Observations: 736

(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)


The following animal species have been reported as pollinators of this plant species or its genus where their geographic ranges overlap: Bombus ternarius (Colla and Dumesh 2010).

  • Literature Cited AboveLegend:   View Online Publication
    • Colla, S.R. and S. Dumesh. 2010. The bumble bees of southern Ontario: notes on natural history and distribution. Journal of the Entomological Society of Ontario 141:39-68.
    • 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
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    • Jones, W. W. 1901. Preliminary flora of Gallatin County. M.S. Thesis. Bozeman, MT: Montana State College. 78 pp.
    • 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.
    • Martinka, R.R. 1970. Structural characteristics and ecological relationships of male blue grouse (Dendragapus obscurus (Say)) territories in southwestern Montana. Ph.D Dissertation. Bozeman, MT: Montana State University. 73 p.
    • Morgan, J.T. 1993. Summer habitat use of white-tailed deer on the Tally Lake ranger district, Flathead National Forest. Ph.D. Dissertation. Montana State University, Bozeman. pp. 103.
  • Web Search Engines for Articles on "Western Trillium"
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Citation for data on this website:
Western Trillium — Trillium ovatum.  Montana Field Guide.  .  Retrieved on , from