Gen. Sp. Orchid. Pl., 294. 1835.
Plants 32–112 cm. Leaves several to many, ascending, scattered along stem, imperceptibly reduced to bracts distally; blade lanceolate to ovatelanceolate, usually to 20 × 4 cm. Spikes lax to moderately dense. Flowers resupinate, showy, corolla white, calyx green to whitish green; lateral sepals porrect; petals obovate to rarely flabellate, apically lacerate; lip descending to horizontally projecting, deeply 3-lobed, without basal thickening, 14–22 × 15–29 mm, distal margins of lobes deeply incised, fringed, lateral lobes flabellate, usually broad, overlapping middle lobe, middle lobe flabellate, sometimes very broadly, emarginate; spur slenderly clavate, 28–47 mm; rostellum lobes nearly parallel, directed downward, short, rounded; pollinaria geniculate; pollinia directed forward (column appearing hooded), remaining enclosed in anther sacs; viscidia orbiculate; ovary slender, mostly 15–30 mm. 2n = 42.
Phenology: Flowering Jun–Aug.
Habitat: Mesic to wet prairies, marshes, fens, lake shores, old fields
Elevation: 80–300 m
Ont., Ill., Ind., Iowa, La., Maine, Mich., Mo., Nebr., N.J., N.Y., Ohio, Okla., Va., Wis.
Of conservation concern.
A very rare hybrid with Platanthera psycodes, known only from Ontario, is P. ×reznicekii Catling, Brownell & G. Allen.
See the discussion under 22. Plantanthera praeclara.
"broad" is not a number.