The common holiay cacti (Thanksgiving Cactus, Christmas Cactus, Easter Cactus) are composed of several closely related species in the genus Schlumbergera and the species Hatiora gaertneri, (often called "Zygocactus" in older works). They are originally forest cacti, growing as epiphytes at elevations between 1000 and 1700 meters above sea level (3280 to 5575 feet above sea level) in the Organ Mountains north of Rio de Janeiro in southeast Brazil, South America (not to be confused with the Organ Mountains of New Mexico in the United States of America). They are called "Flor de maio" (May Flower) in Brazil.