5. Platanthera leucophaea (Nutt.) Lindl. (eastern prairie fringed orchid)

Pl. 116 a; Map 476

Habenaria leucophaea (Nutt.) A. Gray

Flowering stems 40–120 cm long, the flowers 18–30 in a loose raceme. Main stem leaves 3–6. Sepals 7.0–8.5 mm long, the upper sepal slightly shorter than the lateral ones, light greenish white. Lateral petals 8–11 mm long, broadly obovate to broadly spathulate, the tips broadly rounded, rarely shallowly indented, sharply toothed or with a short fringe, white. Lip 16–20 mm long, 3‑lobed, the lobes broadly fan‑shaped, deeply fringed, white. Spur 20–40 mm long, 1.5–2.0 mm in maximum diameter. Column 3.5–4.5 mm long, white, the viscidia 1.2–3.2 mm apart, positioned so as to face each other. 2n=42. June–July.

Uncommon, known only from historical collections from eastern Missouri (northeastern U.S. and adjacent Canada west to Nebraska and Oklahoma). Mesic upland prairies to wet bottomland prairies, usually on calcareous substrates; also recorded from fens and marshes.

This orchid has been extirpated throughout a large portion of its former range, due primarily to the plowing of many prairies for conversion to agriculture and the heavy grazing of other sites by livestock. It is presently listed as Threatened by the U.S. Fish and Wildlife Service under the federal Endangered Species Act. There are no known extant sites in Missouri. The plants emit a sweet fragrance, particularly around sunset, and are pollinated by sphinx moths. For further discussion on the separation of P. leucophaea from the closely related P. praeclara, see the treatment of that species.