Corallorhiza trifida Châtel.

Corallorhiza trifida is largely autogamous, although a syrphid fly (Syrphus cinctellus) was reported as a pollinator by F. Silen (1906). Various floral morphs exist, some with weak geographic correlation; they do not appear to warrant taxonomic recognition. Variants of C. odontorhiza, C. wisteriana, and C. maculata without red and purple pigments in sepals and petals are occasionally misidentified as C. trifida.

Stems ± strongly thickened, base not bulbous. Inflorescences: racemes lax to dense, 8–35 × 1–3 cm. Flowers 3–18, inconspicuous; perianth open; sepals spreading, yellowish to green, lanceolate, 1-veined, 3.5–7 mm; lateral sepals often strongly recurved; petals arching over and clasping column, light yellow-green, often spotted with purple, lanceolate, 1-veined, 3–5.5 mm; lip white, often purple spotted, 2.5–4 × 1.5–3 mm, thin, with 2 small lateral lobes or teeth, middle lobe oblong, often somewhat dilated near apex, with 2 distinct basal lamellae; column curved toward lip, yellowish green, sometimes spotted purple basally, with shallow adaxial channel, 2–3.3 mm; ovary 2.1–6.5 mm; mentum inconspicuous. Capsules ellipsoid, 4.5–15 × 4.3–6 mm. 2n = 42.

Greenland; St. Pierre and Miquelon; Alta., B.C., Man., N.B., Nfld. and Labr., N.W.T., N.S., Nunavut, Ont., P.E.I., Que., Sask., Yukon; Alaska, Calif., Colo., Conn., Del., D.C., Idaho, Ill., Ind., Maine, Md., Mass., Mich., Minn., Mont., N.H., N.J., N.Mex., N.Y., N.Dak., Ohio, Oreg., Pa., R.I., S.Dak., Utah, Vt., Wash., W.Va., Wis., Wyo.; Eurasia.

Flowering spring--summer.

Coniferous, deciduous, and mixed woods, swamps, mountain woods, upland habitats northward, restricted to cool, moist habitats southward; 0--3100m.

Corallorhiza corallorhiza (Linnaeus) MacMillan; C. corallorhiza var. coloradensis Cockerell; C. innata R. Brown; C. innata var. virescens Farr; C. trifida var. verna (Nuttall) Fernald; C. trifida var. virescens (Farr) Fernald; C. verna Nuttall; C. wyomingensis Hellmayr & K. Hellmayr