Christmas cactus purple flower blooms on a black background.. Cacti are believed to have evolved in the last 30 to 40 million years ago. Like many tropical cacti, Christmas Cactus is also an epiphyte. The flowers are available in a wide variety of colors including red, purple, orange, pink, fuschia, cream, etc. Christmas cactus is a member of a group sold as holiday cacti that also includes Thanksgiving cactus and the Easter cactus. The green, flattened, leaf-like structures that make up the majority of a Christmas Cactus are actually modified stem segments called cladodes. In most cacti, the leaves have been modified into spines which have many different functions for the plant. In the Christmas Cactus, the leaves and spines are absent.