Prosthechea is a genus of epiphytic orchids in the family Orchidaceae, commonly known as appendage orchids. It comprises approximately 23 accepted species distributed across the Neotropics, from Mexico south to Paraguay, with additional occurrences in Florida and the West Indies.
Plants grow as epiphytes — anchored to trees rather than soil — with roots covered by a multilayered velamen that absorbs moisture and nutrients from the surrounding air. The erect stems develop into flattened or thickened pseudobulbs bearing one to three terminal, sessile leaves with a leathery, ovate to lanceolate blade. Flavonoid crystals are present in both the roots and leaves.
Flowers are arranged in an apical, paniculate raceme with a spathe at the base of the inflorescence. The genus shows considerable floral diversity: blooms may be borne on a peduncle or sessile, may open simultaneously or in succession along the raceme, and may be resupinate (twisted 180°) or, notably in Prosthechea cochleata, non-resupinate, giving that species its distinctive upside-down appearance. Sepals are nearly equal in length; petals are often more slender. The lip is closely adnate to the proximal half of the column and bears a callus. The column is 3- to 5-toothed at its tip and carries four nearly equal, inversely egg-shaped pollinia. Fruits are 3-winged, ellipsoid to ovoid capsules.
Prosthechea was reestablished as a distinct genus by W. E. Higgins in 1997 (published 1998), drawing species previously scattered across Anacheilium, Encyclia, Epidendrum, Euchile, Hormidium, and Pollardia. Its generic status was subsequently confirmed by molecular phylogenetic analyses of nuclear (nrITS) and plastid (matK, trnL-F) DNA sequences published by Higgins and colleagues in 2003. The genus is abbreviated Psh. in the horticultural trade.
Etymology
The name Prosthechea derives from the Greek word prostheke, meaning "appendage," in reference to the distinctive appendage found on the back of the column in flowers of this genus. The common name "appendage orchid" reflects the same feature. The genus is abbreviated Psh. in horticultural usage.
Distribution
Prosthechea is a neotropical epiphytic genus with a broad range spanning from Mexico south through Central America to Paraguay, and also occurring in Florida and the West Indies.
Taxonomy Notes
Prosthechea was reestablished as a distinct genus by W. E. Higgins in 1997 (published 1998), after its species had been distributed among Anacheilium, Encyclia, Epidendrum, Euchile, Hormidium, and Pollardia. Two species were subsequently transferred to the related genus Euchile (E. citrina and E. mariae) by Withner in 1998; the sister relationship of Euchile to the rest of Prosthechea was confirmed in Higgins's 2000 doctoral dissertation. Generic boundaries were further supported by nuclear (nrITS) and plastid (matK, trnL-F) molecular data (Higgins et al. 2003).
Cultivation
Prosthechea species are grown as ornamental orchids, particularly P. cochleata (the clamshell orchid), which is cultivated widely for its unusual non-resupinate flowers. As epiphytes, they are typically grown mounted on bark or in well-draining orchid bark mixes with bright indirect light and regular moisture during the growing season. The genus is abbreviated Psh. in the horticultural trade.
