Med. Repos., hexade 2, 5: 357. 1808.
Herbs, clonal, rhizomatous, 4–40 cm. Stems purplish to brownish green, glaucous; scales 2–4, typically below soil line, purplish. Leaves green adaxially; blade oblong-lanceolate, obovate, or elliptic, 25–100 × 10–53 mm, apex obtuse to acuminate, sometimes glaucous abaxially. Flowers pedunculate, showy, sweetly fragrant, without nectar; sepals spreading, purplish brown, narrowly lanceolate, 34–67 × 2–4 mm; petals yellowish green, elliptic-obovate to elliptic-lanceolate, 15–25 × 3–7 mm; lip yellowish green to white, streaked with purple, oblong, 15–25 × 8–9 mm, lateral lobes streaked with purple, margins involute, middle lobe rounded, margins revolute, undulate; callus green, longitudinal, fleshy; column 8–12 mm; ovary 20–30 mm; rostellar flap prominent. Capsules 20–42 × 5–10 mm; pedicel of mature capsule elongating to 20–55 mm. 2n = 18.
Phenology: Flowering Apr–Jun.
Habitat: Acidic soils, in dry to mesic forests, seeps, sphagnum bogs
Elevation: 10–2000 m
Ont., Ala., Ark., Conn., Del., Fla., Ga., Ill., Ind., Ky., La., Maine, Md., Mass., Mich., Miss., Mo., N.H., N.J., N.Y., N.C., Ohio, Okla., Pa., R.I., S.C., Tenn., Tex., Vt., Va., W.Va.
Isotria verticillata frequently forms extensive clones with hundreds of stems. It is pollinated by solitary bees of the Andrenidae, Anthophoridae, and Halictidae; plants are apparently self-compatible (L. A. Mehrhoff 1983). Nonflowering plants only rarely have a white, arrested floral bud (1–2 mm).