'Schlumbergera' is a small genus of cacti with six to nine species found in the coastal mountains of south-eastern Brazil. Plants grow on trees or rocks in habitats that are generally shady with high humidity, and can be quite different in appearance from their desert-dwelling cousins.

Common names for these cacti generally refer to their flowering season. In the Northern Hemisphere, they are called Christmas cactus, crab cactus and holiday cactus. In Brazil, the genus is referred to as 'Flor de Maio' (May flower), reflecting the period in which they flower in the Southern Hemisphere.

Most of the popular houseplants are cultivars of Schlumbergera, rather than species, with flowers in white, pink, yellow, orange, red or purple. The fruits 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.

Plants are offered for sale under a variety of common names. The earliest English common name was "Christmas cactus". In Europe, where plants are largely produced for sale in the period before Christmas, this remains the most widely used common name in many languages for cultivars of all groups. This is also the name used in Canada.

More Info: en.wikipedia.org