Plant 365

Schlumbergera species (Cactaceae)

Christmas cactus

The genus Schlumbergera comprises about nine species found in coastal montane regions of south-eastern Brazil. Schlumbergera belongs to a tribe of cacti, the Rhipsalideae, which unlike most cacti, grow on trees and rocks in shady, humid habits. The generic name probably commemorates the nineteenth-century French horticulturalist Frédéric Schlumberger, who contributed ‘judicious and interesting communications on the flowers of the cacti’ to the Revue horticole.

Most Schlumbergera species have flattened green stems, arranged in segments, with clusters of soft bristles at the end of each segment, from where the flower buds arise. The large, nectar-producing, hummingbird-pollinated flowers are usually red or pink, and tubular in form. When successfully pollinated and fertilised, flowers produce fleshy fruits which show adaptations for dispersal by fruit-eating birds.

Horticulturally, the two best-known members of the genus are Schlumbergera truncata and Schlumbergera russellianus, both of which are distributed in the Atlantic forest of the Serra dos Órgãos, close to Rio de Janeiro. Schlumbergera truncata is found in a narrow band approximately 700-1,000 metres above sea level, whilst Schlumbergera russellianum occurs from 1,400 metres to 2,100 metres above sea level. However, the natural distributions of both species are unclear because they are often planted as ornamentals.

Schlumbergera truncata was first described by the English naturalist Adrian Haworth in 1819 from a plant cultivated at Kew. The species was widely grown in the succulent collections of European horticulturalists before this date. In contrast, the route of introduction of Schlumbergera russellianum into horticulture is known. In the late-1830s, the Scottish botanist and surgeon George Gardner was supported by men such as William Hooker, Professor of Botany at the University of Glasgow and later Director of Kew, and John Russell, sixth Duke of Bedford, to collect plants in Brazil. In early 1837, Gardner was collecting in forests near modern Teresópolis, and found an epiphytic, cerise-flowered cactus, like the one he knew from British glasshouses. He could hardly contain his enthusiasm at the prospect that this new cactus might fill European glasshouses. He packed Wardian cases with living plants for the garden of his Lordship and Glasgow Botanic Garden, and asked Hooker to name the plant in Russell’s honour.

By the early 1850s, horticulturalist William Buckley had crossed the two species to produce the familiar Christmas cactus. Today, hundreds of colourful cultivars and complex hybrids, raised from crosses involving Gardner’s introduction, are spread around the world, filling the world’s homes and glasshouses.

Further reading

Calvente A et al. 2011. Molecular phylogeny of tribe Rhipsalideae (Cactaceae) and taxonomic implications for Schlumbergera and Hatiora. Molecular Phylogenetics and Evolution 58: 456-468.

Gardner G 1838. XVII. An account of a journey to, and a residence of nearly six months in, the Organ Mountains, with remarks on their vegetation. Annals of Natural History 1: 165-181.

McMillan AJS and Horobin JF 1995. Christmas cacti: the genus Schlumbergera and its hybrids. David Hunt.

Stephen Harris