Distribution: Occurring east of the Cascades crest in eastern Washington; south-central British Columbia and southwestern Alberta to central Idaho and western Montana, disjunct in Wyoming and Colorado.
Habitat: Moist woods.
Flowers: April-July
Origin: Native
Growth Duration: Perennial
Conservation Status: Not of concern
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PNW Herbaria: Specimen records of Trillium stenosepalum in the Consortium of Pacific Northwest Herbaria database
WA Flora Checklist: Trillium stenosepalum checklist entry
OregonFlora: Trillium stenosepalum information
E-Flora BC: Trillium stenosepalum atlas page
CalPhotos: Trillium stenosepalum photos