Epiphytes or terrestrial (occasionally lithophytic) herbs. Stem usually tufted or matted, leafy toward apex, branching from a rooting base, non-pseudobulbous. Leaves distichous, terete or laterally compressed, articulated on their often papillose or verrucose sheaths, sometimes fleshy, often verrucose, obtuse to acute. Inflorescence lateral on upper part of stem, racemose, spiciform, secund, often nodding distally, rachis often flexuose, sometimes flattened. Flowers resupinate, often fleshy, greenish yellow, green, or orange. Sepals and petals free or basally connate, spreading. Sepals oblong, obtuse, glabrous. Petals smaller and usually narrower than sepals, linear or obovate-spathulate, densely papillose, minutely puberulus or glabrous. Labellum entire, sessile at base of column, oblong, concave, sometimes uncinate, glabrous or puberulus; disc often with two longitudinal, basal calli. Column glabrous or puberulus, often ventricose and hollow in front and enclosing stigma, rarely with a large, entire or bilobed basal appendage, with or without stelidia, stelidia usually densely papillose, falcate or oblong, curved inward over anther, foot absent; pollinia eight, unequal, occasionally four, borne on caudicles; rostellum well developed. (JW).
Species have been recorded growing in a variety of habitats from 300 to 4000 m as epiphytes among mosses and liverworts on trunks and branches in several types of forests: upper and lower montane, oak/laurel, montane Dipterocarpaceae/Agathis Salisb. (Podocarpaceae), Lithocarpus Blume (Fagaceae), scrubby Lithocarpus/Myrtaceae, open kerangas on podsolic soil, Podocarpus/ Phyllocladus Rich. (Podocarpaceae), and open and dry forests on steep sandstone ridges. They may also occur on branches of Vaccinium (Ericaceae) on ridges, subalpine shrubberies, and tree trunks in subalpine grassland. Species such as O. lorentzii J. J. Sm. have been reported in New Guinea as terrestrial in mossy ground under Papuacedrus Li (Cupressaceae) and in stunted, mossy, upper montane forest on limestone and in Nothofagus Blume (Nothofagaceae)/Myrtaceae forest. Octarrhena bilabrata (P.Royen) W.Kittr. was recorded as epiphytic on Cordyline terminalis (L.) Kunth (Asparagaceae) and Octarrhena suborbicularis ( J. J. Sm.) P.Royen growing in rock crevices, both in Papua New Guinea. (JW).