Holiday Cactus - Distribution, Habitat and Ecology

Distribution, Habitat and Ecology

Schlumbergera occurs only in the coastal mountains of south-east Brazil, in the states of São Paulo, Rio de Janeiro, Minas Gerais and Espírito Santo. Sites where it has been found range from close to the Tropic of Capricorn northwards to 20°S, i.e. in the southernmost part of the tropics. Plants grow at altitudes from 700 metres (2,300 ft) in the case of S. truncata to 2,780 metres (9,120 ft) in the case of S. microsphaerica, either in the coastal moist forests or in rocky areas. The natural distribution of Schlumbergera species has become confused because European cultivars were deliberately introduced into some areas, including the Parque Nacional da Serra dos Órgãos, by the Brazilian Agricultural Department, to compensate for over-collecting of wild plants.

Because of their height and proximity to the Atlantic Ocean, the coastal mountains produce high altitude moist forests – warm moist air is forced upwards into higher, colder locations where it condenses. Schlumbergera species grow in habitats which are generally relatively cool, shaded and of high humidity. David Hunt describes collecting specimens in conditions of cloud, drizzle and overnight temperatures down to −4 °C (25 °F). Plants are epiphytic or lithophytic, growing on moss-covered tree branches or in rock crevices, often in small pockets of substrate formed from decayed leaves and other vegetation. S. microsphaerica is found at higher altitudes, above 2,200 metres (7,200 ft), in barren rocky habitats, and tolerates higher light levels.

The flowers of Schlumbergera have adaptations for pollination by hummingbirds: tubular flowers with abundant nectar, and colours towards the red end of the spectrum. Most species require cross-pollination to set seed. The exceptions are S. kautskyi and S. microsphaerica; as noted above, the latter is found at higher altitudes where humming birds may be absent or less common.

The fruits of Schlumbergera do not open spontaneously when ripe, and appear to be adapted for distribution by birds, which eat the seeds and pulp contained in the fruit. Birds have been observed removing seeds which had stuck to their beaks by rubbing them on tree branches, where the seeds might be able to germinate. Segments may also break off from the stems and take root, thus enabling plants to propagate vegetatively.