Orchis flava Linnaeus, Sp. Pl. 2: 942. 1753; Habenaria flava (Linnaeus) R. Brown; Perularia scutellata (Nuttall) Small

Plants 13–65 cm. Leaves (1–)2–3(–4), spreading to ascending, gradually to rather abruptly reduced to bracts distally; blade lanceolate to elliptic-oblong, 5–35 × 1–7 cm. Spikes lax to dense. Flowers resupinate, inconspicuous, yellowish green; lateral sepals porrect to reflexed; petals oblong-orbiculate to ovate, apex somewhat crenulate; lip descending to commonly reflexed, 2–6 × 1.8–5 mm, base auriculate, with prominent central tubercle, distal margin entire to slightly crenulate; spur cylindric to strongly clavate, 4–8(–11) mm, apex rarely 2-lobed; rostellum lobes mostly parallel to slightly diverging, directed downward, minute, obscure; pollinia remaining enclosed in anther sacs; viscidia mostly quad-rangular, oblong-quadrangular, orbiculate, or broadly asymmetric, commonly canaliculate to nearly cylindric and difficult to assess; ovary rather slender to stout, mostly 8–10 × 2 mm.

Varieties 2 (2 in the flora): e North America.