Hatiora is a small genus of epiphytic cacti in the family Cactaceae, order Caryophyllales, belonging to the tribe Rhipsalideae within the subfamily Cactoideae. The genus comprises a handful of species native exclusively to the Mata Atlântica (Atlantic Forest) of eastern Brazil, where they grow on trees as epiphytes or, rarely, on rocks as lithophytes.
All Hatiora species share a distinctive appearance quite unlike most cacti: the plants are weakly succulent and grow more or less upright, becoming woody at the base with age. Their stems are round in cross-section, typically divided into short cylindrical segments, and spines are usually absent. Flowers are borne terminally, are small (about 2 cm in diameter), actinomorphic (radially symmetrical), and bell-shaped, appearing in shades of yellow, yellow-orange, or pink. The fruit is a berry.
The genus has a complex taxonomic history. The first species was described by Haworth in 1819 as Rhipsalis salicornoides; in 1834, A.P. de Candolle recognised its distinctness and moved it to a new genus Hariota, named after Thomas Hariot, a 16th-century English botanist. In 1923, Britton and Rose created the name Hatiora as a taxonomic anagram of Hariota to resolve nomenclatural confusion. Subsequent molecular phylogenetic studies reorganised the genus further: three species formerly in subgenus Rhipsalidopsis — including the widely grown Easter cactus (formerly Hatiora gaertneri) — have since been transferred out of Hatiora into either Rhipsalidopsis or a broadly circumscribed Schlumbergera. The core Hatiora is now distinguished chiefly by its round cylindrical stems and radially symmetrical flowers.
The best-known species, Hatiora salicornioides, is a popular ornamental succulent prized for its cascading bottle-brush-like segments and small orange-yellow flowers.
Etymology
The name Hatiora was coined in 1923 by Nathaniel Britton and Joseph Rose as a taxonomic anagram of the earlier genus name Hariota. Hariota had been established by A.P. de Candolle in 1834, honouring Thomas Hariot (also spelled Harriot), a 16th-century English botanist and explorer.
Distribution
All Hatiora species are native to eastern Brazil, growing in the tropical rainforests of the Mata Atlântica (Atlantic Forest). Within this biome they live as epiphytes on trees or, occasionally, as lithophytes on rocks.
Taxonomy Notes
Hatiora belongs to the tribe Rhipsalideae within the cactus subfamily Cactoideae — a group of epiphytic cacti quite distinct in appearance from most other cacti. The genus underwent significant revision following DNA-based phylogenetic studies: three species placed by Barthlott and Taylor (1995) in the subgenus Rhipsalidopsis — H. gaertneri, H. rosea, and H. epiphylloides — are now generally transferred out of Hatiora. There is broad agreement that H. epiphylloides belongs in Schlumbergera (as S. lutea), while the placement of the other two remains disputed between a broadly circumscribed Schlumbergera and the reinstated genus Rhipsalidopsis. The core Hatiora retains a small number of species characterised by cylindrical stems and actinomorphic flowers.
Cultivation
Hatiora species, particularly H. salicornioides, are grown as ornamental houseplants. As epiphytic cacti from tropical rainforests they differ markedly from desert cacti in their cultural requirements: they prefer bright indirect light, moderate humidity, and a well-draining but moisture-retentive growing medium. They are sensitive to frost and are grown as indoor plants outside tropical climates.
