Terrestrial or very rarely epiphytic plants with root-stem tubers or fleshy, short to long rhizomes, rarely mycotrophic with leaves reduced to colorless sheaths. Tubers, if present, ovoid, spherical, ellipsoidal, digitate, or cylindric-fusiform, solitary or in clusters, hairy or glabrous; rhizome, if present, fleshy, elongate. Leaves spirally arranged, 1 to many, basal or arranged along stem, deciduous or rarely persistent for more than a year, often sheathing at base, usually green, rarely spotted or veined with silver, red, or gold, rarely purple spotted or shaded beneath. Inflorescence terminal, erect or arching, 1- to many flowered; peduncle usually terete, glabrous, hairy, or glandular; bracts linear, lanceolate, ovate, or elliptic, usually glabrous and green. Flowers small to large, usually resupinate, flat to tubular, often showy; pedicel often obscure; ovary distinct, glabrous or less frequently hairy or glandular, lacking an abscission layer. Dorsal sepal free or often adnate to petals to form a hood over column; lateral sepals usually free, sometimes connate and oblique at base to form a spurlike mentum. Petals entire or 2-lobed, often adnate to dorsal sepal; lip usually lowermost in flower, usually deflexed, entire, 3- or 5-lobed, or 2-partite, occasionally callose or with 2 basal glands, often saccate at base or with spurlike nectary; nectary fusiform, clavate, or cylindric, rarely fused to ovary, often lacking nectar. Column basifixed or not; anther 2-locular, longer than or as long as rostellum, locules adnate, divergent, or separated on a ± broad connective; pollinia 2 or 4, sectile, attached by short to elongate caudicles to 1 or 2 viscidia; staminodes 2, lateral, usually present, sessile or stalked; stigma entire or 2-lobed, sessile or stalked, concave to convex; rostellum usually 2- or 3-lobed, shorter than or as long as anther, sometimes obscure, when 3-lobed mid-lobe erect or porrect, lying between or in front of anther locules, side lobes short to long, porrect, rarely incurved or upcurved. Capsule 3-ribbed, longitudinally dehiscent. Seeds fusiform to almost cylindric, with a thin testa.
About 192 genera and ca. 3,630 species in eight tribes and 20 subtribes: well represented in N temperate and tropical areas of both the Old and New Worlds; 46 genera (four endemic, one introduced) and 344 species (153 endemic, one introduced) in China.
This subfamily is particularly well represented in temperate parts of China.