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MONTANA FIELD GUIDE™

MONTANA FIELD GUIDE™

Western Trillium - Trillium ovatum

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Native Species

Global Rank: G5
State Rank: S4S5
(see State Rank Reason below)
C-value: 6


Agency Status
USFWS:
USFS:
BLM:


 





State Rank Reason (see State Rank above)
DRAFT: Requesting feedback on the 2026 revised rank, factors, and State Rank Reason outlined below and in the Conservation Status Rank Report. Trillium ovatum is locally common in some mesic forests in western Montana. No significant and widespread threats to the species are known. Population levels are robust enough that its viability in the state is not a concern, though various life history and reproductive characteristics may limit its ability to recover or repopulate areas following severe disturbance.
Western Trillium (Trillium ovatum) Conservation Status Summary
State Rank: S4S5
Review Date = 06/29/2026
See the complete Conservation Status Rank Report
How we calculate Conservation Status Ranks
CC BY NC
 
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 in Montana
CC BY NC
Native
 


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: 871
(Click on the following maps and charts to see full sized version)
Relative Density

Recency

 

(Observations spanning multiple months or years are excluded from time charts)



Habitat
Predicted Suitable Habitat Model

This species has a Predicted Suitable Habitat Model available.

To learn how these Models were created see here

Ecology
POLLINATORS
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).


References
  • 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
    Do you know of a citation we're missing?
    • 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