Epiphyllum is a genus of about 10 accepted species of cacti in the family Cactaceae, tribe Hylocereeae, commonly known as orchid cacti, climbing cacti, or leaf cacti. The genus was established in 1812 by Adrian Hardy Haworth, who named it from the Ancient Greek epi- ("upon") and phúllon ("leaf"), referring to the distinctive flattened, leaf-like stems on which the flowers appear to sit.
These are epiphytic shrubs, erect to pendent and many-branched, growing naturally upon trees and occasionally rocks in humid tropical and subtropical forests rather than in soil. The segmented stems are broadly flattened and elongate, measuring 50 cm to well over a metre in length, with a prominent midvein-like axis and lobed or crenate margins; adult stems are spineless. The overall impression — a flat, leaf-like structure bearing large flowers — gives the genus its common name of leaf cactus.
Flowers are among the most spectacular in the cactus family. They are funnel- to salverform with a long, slender tube and measure 8–38 cm across. Most species are nocturnal, opening after dark and wilting by dawn, and are predominantly white or cream, sometimes with outer tepals tinged red or pink. The combination of large white blooms, a long floral tube, copious nectar, and a strong fragrance strongly suggests hawkmoth pollination. Epiphyllum oxypetalum is particularly celebrated for its large, strongly fragrant nocturnal flowers, and is cultivated worldwide as an ornamental.
Fruits are fleshy, splitting along one side at maturity, and range in colour from light green through red to purple, resembling a small pitaya. Seeds are black and kidney-shaped. The base chromosome number is x = 11.
The genus is native from Mexico through Central America to northern and northeastern South America and the Caribbean. Several species, including E. hookeri and E. oxypetalum, have been introduced outside their native range, reaching southern China, Vietnam, Pacific islands, and parts of the Caribbean. Recognised synonyms include Phyllocactus Link and Marniera Backeb.
The popular "orchid cacti" of horticulture are intergeneric hybrids within tribe Hylocereeae, mainly involving species of Disocactus; actual Epiphyllum parentage in most commercial cultivars is unconfirmed.
Etymology
The genus name Epiphyllum is formed from two Ancient Greek elements: epi- (ἐπι-), meaning "upon" or "on top of," and phúllon (φύλλον), meaning "leaf." The name alludes to the flowers appearing to arise directly from the flattened, leaf-like stems, as if blooming upon a leaf. The genus was formally published under this name by Adrian Hardy Haworth in Syn. Pl. Succ.: 197 in 1812.
Distribution
Epiphyllum is native from Mexico southward through Central America to northern and northeastern South America, including the Caribbean. Individual species ranges vary: Epiphyllum phyllanthus spans the widest range from Mexico to Argentina, while Epiphyllum oxypetalum is concentrated in Belize, Honduras, El Salvador, and Mexico. Epiphyllum hookeri occurs in Mexico, Central America, and Venezuela and has been introduced to Florida. Beyond its native range, the genus has been introduced to southern China, Vietnam, Pacific islands, and parts of the Caribbean, largely as a result of cultivation.
Ecology
Epiphyllum species grow as epiphytic shrubs in humid tropical and subtropical forests, attaching themselves to trees or occasionally rocks rather than rooting in soil. Their spineless, flattened stems are adapted to life in the forest canopy where light filtering through the canopy drives their characteristic elongate growth form.
Flowers open nocturnally — after dark and wilting before dawn — and their combination of large white or cream blooms with a long, slender floral tube, copious nectar production, and strong fragrance is characteristic of hawkmoth (sphingid) pollination syndrome. Fleshy, brightly coloured fruits (green to red or purple) suggest bird or mammal dispersal of the kidney-shaped black seeds.
Cultivation
Epiphyllum species are cultivated as ornamentals for their spectacular flowers, particularly Epiphyllum oxypetalum, which is grown worldwide. In horticulture, the name "orchid cactus" is commonly applied to the large group of intergeneric hybrids in tribe Hylocereeae, though these are primarily derived from Disocactus rather than true Epiphyllum species. True Epiphyllum species prefer bright indirect light, well-draining but moisture-retentive substrates suited to epiphytes, and protection from frost in temperate climates.
Taxonomy
The genus Epiphyllum was established by Adrian Hardy Haworth and published in Syn. Pl. Succ.: 197 (1812). The type species is Epiphyllum phyllanthus (L.) Haw. It belongs to tribe Hylocereeae within subfamily Cactoideae, family Cactaceae, order Caryophyllales. POWO and GBIF both recognise approximately 10 accepted species, though some regional treatments list more (SEINet lists 16 in their checklist).
Four synonyms are recognised by POWO, the most significant being Phyllocactus Link and Marniera Backeb. The IPNI identifier for the genus is urn:lsid:ipni.org:names:30002688-2. The base chromosome number is x = 11.
The plants commonly sold and exhibited as "orchid cacti" (epiphyllum hybrids) are intergeneric hybrids within tribe Hylocereeae, predominantly involving species of Disocactus. Actual Epiphyllum species involvement in the parentage of most commercial cultivars remains unconfirmed.
