Distribution: Occurring east of the Cascades crest in Washington; Washington to northeastern Oregon, east to Idaho.
Habitat: Stream banks, moist meadows, forest edge, and thickets at low to middle elevations in the mountains.
Flowers: April-June
Origin: Native
Growth Duration: Perennial
Conservation Status: Not of concern
Glabrous perennial herbs from short, thick rhizomes, the annual stems largely subterranean, 5-18 cm. long.
Leaves 3, whorled, not mottled, long-petiolate; leaf blade nearly orbicular to broadly ovate, rounded or nearly cordate at the base, rounded at the tip, 8-13 cm. long and wide.
Flower solitary, sessile; sepals 3, green, narrowly oblong-elliptic, 2.5-6 cm. long; petals 3, usually reddish-purple, but sometimes yellowish, greenish or brownish, about the same size and shape as the sepals; stamens 6, filaments 1-3 mm. long, anthers 10-30 mm. long, purple.
Fruit a fleshy capsule.
PNW Herbaria: Specimen records of Trillium petiolatum in the Consortium of Pacific Northwest Herbaria database
WA Flora Checklist: Trillium petiolatum checklist entry
OregonFlora: Trillium petiolatum information
E-Flora BC: Trillium petiolatum atlas page
CalPhotos: Trillium petiolatum photos