Disocactus is a genus of epiphytic cacti belonging to the family Cactaceae, placed in the tribe Hylocereeae within the order Caryophyllales. The genus encompasses roughly 28 accepted species native to tropical regions of Central America, the Caribbean, and northern South America, where they grow as epiphytes clinging to the branches of trees or as lithophytes on rocky outcrops.
Plants are shrubby and profusely branched, with trailing or hanging stems that can reach up to 3 metres in length. The shoots are characteristically flattened and ribbon-like, typically 3–10 mm wide, with remotely crenate margins — a form convergently similar to leaves though botanically these are modified stems. In some species, such as Disocactus phyllanthoides, the main shoot is round at the base but transitions to a fully flattened, leaflike form toward the tip; lateral shoots are entirely flattened.
Flowers are large and showy, measuring 10–15 cm long, and open during the day. They are funnel-shaped or tubular, sometimes zygomorphic (bilaterally symmetrical), and come in striking colours including bright red, orange, reddish-pink, pale yellow, and white. The stamens are characteristically arranged in an asymmetric cluster along the lower side of the perianth throat, and the style is notably exserted, extending 9–13 cm with 8–9 stigma lobes. The berry-like, ellipsoid fruits reach up to 7 cm long and contain small, brown-black seeds.
Disocactus is closely related to the genus Epiphyllum, and many plants sold commercially as "epiphyllum hybrids" are in fact hybrids involving Disocactus species crossed with other members of the Hylocereeae. The genus should not be confused with Discocactus, a distinct genus of globose cacti. Aporocactus (the rat-tail cactus group) was historically included within Disocactus but molecular evidence supports treating it as a separate genus; Pseudorhipsalis is also sometimes merged into Disocactus but is kept separate by the International Cactaceae Systematics Group.
Distribution
Disocactus species are native to Central America, the Caribbean, and northern South America. They grow in tropical habitats, either as epiphytes on trees or as lithophytes on rocky surfaces.
Ecology
Species of Disocactus inhabit tropical forests as epiphytes growing on tree branches, or as lithophytes on rocky outcrops. Their flattened, ribbon-like stems are adapted to life in the forest canopy, where they hang and trail as they capture filtered light.
Cultivation
Many Disocactus species and their intergeneric hybrids — often sold as "epiphyllum hybrids" — are widely grown as ornamentals for their large, colourful flowers. As epiphytes, they do well in well-draining, organic-rich mixes and prefer bright indirect light.
Taxonomy notes
Disocactus belongs to the tribe Hylocereeae within family Cactaceae. Aporocactus (the rat-tail cacti) was formerly included within Disocactus but is supported as a distinct genus by molecular evidence. Pseudorhipsalis is sometimes merged into Disocactus but is kept separate by the International Cactaceae Systematics Group. The genus should not be confused with Discocactus, an unrelated genus of globose cacti.
