Epiphytic or lithophytic, subcaespitose or creeping, erect or pendent herbs. Roots flexuous. Rhizome concealed by scarious, fugaceous sheaths. Pseudobulbs crowded to remote, of a single internode, compressed, fusiform, ellipsoid, ovoid to globular, sessile, surface smooth to rugose-warty, partially concealed by the fugaceous sheaths of the rhizome. Leaf solitary at the apex of the pseudobulb, articulate, conduplicate, fleshy, linear and subulate to ovate-lanceolate and trigonous, sessile to subpetiolate, adaxially sulcate, concolorous greyish green suffused with dark purplish, margins entire to minutely erose-muriculate, surface minutely rugose. Inflorescence terminal, peduncle filiform, emerging from a tubular, conduplicate bract at the apex of the pseudobulb, with few to several internodes, straight to fractiflex, peduncle bracts imbricate to remote, tubular, raceme one-flowered (reported with up to four successive flowers in H. leochilus (Rchb.f.) Rauschert); floral bracts amplexicaul, tubular to funnel-shaped, often conspicuously larger than the other peduncle bracts, smooth to pellucid, shorter than the ovary to subequal. Flowers resupinate, campanulate to widely spreading, small and inconspicuous to large and showy; perianth membranaceous to fleshy, whitish, translucent green, variously suffused and/or dotted with maroon or purple, as far as known not fragrant. Sepals free, subsimilar, spreading to semi-closed, narrowly triangular, lanceolate, ovate or elliptic, rounded to long attenuate, smooth, furfuraceous, or pellucid (H. leochilus). Petals similar to the sepals, free, spreading to semi-closed, straight to arcuate, subclawed or not, ovate-oblong, elliptical, lanceolate, triangular-oblong or oblanceolate, rounded-emarginate to long attenuate, dorsally carinate, margins entire to minutely erose. Labellum clawed or not, free or the claw strongly attached to column foot, the claw transversely oblong-cochleate to oblong-linear, blade entire, panduriform, oblong-ovate, elliptical, suborbicular-quadrate, constricted or not, obtuse-retuse to acuminate, flat or convex, margins entire to minutely serrulate, disc smooth or with a transverse, basal ridge which can be simple or with flabellate, thick, protruding lateral auricles. Column apically broadened, semiterete-arched, either wingless, winged along all its length or sometimes with basal, flabellate or deltate-falcate, incurved auricles at the margins of the column foot, apex with recurved, oblong truncate wings or wingless, clinandrium projected, cucullate, bilobed, often with a longer midtooth, column foot concave and forming a semi-closed chamber or not; anther terminal to incumbent, operculate, imperfectly four-locular, green to reddish, pollinarium with four pollinia, equal, hard, waxy, laterally compressed, united to caudicles that bear two or four additional minipollinia at the other end; stigma ventral, the lateral lobes sometimes protruding and with a conspicuous limiting rim; rostellum a transverse, semi-elliptical, recurved, thick blade. Ovary clavate, smooth, furfuraceous or papillose-muricate. Capsule globose to ellipsoid-trigonous, smooth to muricate. (MS).
Homalopetalum species are from moist to wet montane forests. The widespread complex around H. pumilio is found in moist to wet areas at medium elevations, and it is particularly abundant in oligotrophic forests on granite and quartzic sands. Homalopetalum pumilio is rupicolous or epiphytic, and in some areas it is found on Clusia L. twigs (Clusiaceae). Other species are more decidedly montane. Homalopetalum pumilum is found in cold oak and cloud forests in eastern Mexico, at 1400–2400 m elevation, which experience freezing temperatures in the winter. (MS)