Distribution: Occurring west of the Cascades crest in Washington; Alaska to California.
Habitat: Moist coniferous forest at low elevations.
Flowers: May-June
Origin: Native
Growth Duration: Perennial
Conservation Status: Review Group 1 in Washington (WANHP)
Pollination: Self-pollination, flies
Herbaceous terrestrial perennials, 10-60 cm tall, erect, glabrous; stems unbranched, not angled, not swollen toward base; roots tuberous, few.
Leaves few, prostrate to erect-spreading, ephemeral, basal; blades sessile, lanceolate to oblanceolate, 5-18 cm long and 1.1-3.5 cm broad; cauline bracts ovate to linear-lanceolate.
Inflorescence sparsely flowered raceme, somewhat secund, 10-30 cm; rachis nearly or as long as peduncle; bracts 3-10 mm; flowers white, emit faint fragrance, harsh to honeylike; sepals oblong-elliptic, 1.8-3.5 mm long and 1-1.9 mm broad; dorsal sepal extending outward or somewhat curved; lateral sepals deflexed, slightly twisted; petals typically projecting forward and converging with the others, white with faintly green midvein, unevenly lanceolate, 2-4 mm long and 1 mm broad; labellum curved downward, triangular-ovate, 2-3 mm long and 1-2.8 mm broad; spur curved, attenuate, 1.5-4 mm; viscidia widely elliptic to ovate, 0.3-0.6 mm long and 0.2-0.4 mm broad; rostellum slightly elongate.
Capsules 5-9 mm, erect, subsessile; seeds cinnamon brown.
PNW Herbaria: Specimen records of Platanthera ephemerantha in the Consortium of Pacific Northwest Herbaria database
WA Flora Checklist: Platanthera ephemerantha checklist entry
OregonFlora: Platanthera ephemerantha information
E-Flora BC: Platanthera ephemerantha atlas page
CalPhotos: Platanthera ephemerantha photos