White Bog Orchid - Platanthera dilatata
Stems 15–70 cm. Leaves cauline, 3–20 cm long, lanceolate. Inflorescence dense, 4–25 cm long with 10 to 50+ flowers; bracts 5–40 mm long. Flowers white; lateral sepals 4–8 mm long; hood 4–6 mm long; lip petal 4–9 mm long, broadened at the base, pendent; spur sac-like to slender, curved, 2–12 mm long. Capsule 8–15 mm long (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX
Platanthera dilatata has three varieties in Montana: albiflora, dilatata, and leucostachya (Lesica 2012). They are separated by the length of the spur relative to the lip of the flower. However, these characteristics are variable and cannot be separated based on ecology or geography. This species can also hybridize with other Platanthera species.
Wet soil of meadows, fens, thickets, open forest, often along streams, ditches; valleys to lower subalpine (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX