(Photograph = Rhipsalis sp from Brazil)
Introduction
The subfamily Cactoideae includes mostly arid-adapted cacti. The tribe Rhipsalideae, however, is a small group of four genera that grow in humid habitats. These plants are typically epiphytes (or lithophytes) in tropical rainforests. Although succulent, they are not desert-adapted; instead, they are adapted to the intermittent water scarcity that occurs in the forest canopy between rains.
The Details
The four genera in Rhipsalideae are Hatiora, Lepismium, Schlumbergera, and Rhipsalis. Rhipsalis contains the most species (several dozen), and most members of the tribe have been placed in Rhipsalis at one time or another. Flowers are generally small.
Rhipsalis plants are known as the mistletoe cacti because they can resemble leafless mistletoes and often bear small, white berries; some species have yellow or reddish fruits.
Plant form is variable. Most commonly, they are hanging plants with cylindrical, triangular, or flattened stems. Stems may drape many feet, forming veils of vegetation that cascade from tree limbs.
Some Rhipsalis make good houseplants because they tolerate low light and grow well in small pots.
Other hanging cacti—such as Pseudorhipsalis—belong to the tribe Hylocereeae and are not especially closely related to Rhipsalis.
Additional Reading: Stem Anatomy of Rhipsalis
