Rhipsalis
Rhipsalis is the largest genus of epiphytic cacti — trailing, mostly spineless rainforest plants that grow perched on tree branches rather than in the ground. Widely sold as easy-going hanging houseplants under the common name mistletoe cactus, Rhipsalis is remarkable for being the only cactus group with species native beyond the Americas, reaching tropical Africa, Madagascar and Sri Lanka.
Description
Rhipsalis are shrubby or pendent epiphytes that hang in cascading tangles of thin, soft stems. Unlike the ribbed, spiny desert cacti most people picture, these plants have slender segmented stems that may be cylindrical, flattened and leaf-like, angled, or even chain-like, and are usually smooth and green with few or no spines. In the wild they anchor themselves in the forks and crotches of trees, rooting into pockets of leaf litter and moss high in the canopy.
The flowers are typically small, bell- or star-shaped, and cream to white (occasionally tinged pink or yellow), scattered along the stems. These are followed by small, translucent, berry-like fruits — white, pink or reddish — that closely resemble mistletoe berries and give the genus its familiar common name. The overall effect is soft and ferny rather than fierce, which makes Rhipsalis unusual and appealing among cacti.
Distribution
The genus is centred on the humid forests of Central and South America, especially the Atlantic rainforest of Brazil, where the greatest diversity occurs. What sets Rhipsalis apart from every other cactus genus is its natural range beyond the New World: a handful of populations occur in tropical Africa, Madagascar, the Mascarene Islands and Sri Lanka. These are generally thought to have arrived by long-distance dispersal — most likely seeds carried in the guts of migrating birds — rather than being separately introduced by people.
Across this range the plants are almost always epiphytic or lithophytic (growing on rocks), thriving in warm, shaded, humid conditions with good air movement and dappled light beneath the forest canopy.
Notable species
- Rhipsalis baccifera — the classic mistletoe cactus, with thin trailing green stems and white berries; the widest-ranging species and the one found naturally in the Old World.
- Rhipsalis pilocarpa — softly bristly stems and comparatively large, scented, cream flowers.
- Rhipsalis cereuscula — the "coral cactus", with branching clusters of short, chunky stem segments.
- Rhipsalis campos-portoana — fine, delicate pendent stems that flower freely.
- Rhipsalis paradoxa — the "chain cactus", whose angular stems twist so the segments seem to link like a chain.
Cultivation
Rhipsalis are among the more forgiving cacti to grow indoors, precisely because they are not desert plants. Grow them in bright, indirect light — an east-facing window or a spot shaded from harsh midday sun suits them well — as too much direct sun can scorch or redden the stems, while deep shade produces weak, sparse growth. A hanging basket or a pot on a shelf where the stems can trail freely shows them off best.
Because they are epiphytes, they resent being waterlogged. Pot them in a light, open, airy medium — many growers use an orchid-style or coarse mix with plenty of bark and grit — and water more often than you would a desert cactus, letting only the top of the mix dry between waterings. They appreciate humidity and warmth, dislike cold, and should be kept above about 10 °C. See Watering and Repotting for general technique, and note that a slightly cooler, drier spell in winter can help encourage flowering.
Hobby and cultivar notes
Rhipsalis has surged in popularity as a low-fuss trailing houseplant, and stems root very readily, so plants are usually shared and multiplied from cuttings: a segment laid on or pushed into moist mix will strike roots with little effort. They can also be raised from the small seeds inside the berries (see Propagation — seed). The genus is closely allied to other epiphytic cacti such as Hatiora, Lepismium and Schlumbergera (the Christmas cactus), and the boundaries between these groups have been repeatedly reshuffled by botanists, so plants are sometimes sold under older or conflicting names. Named cultivars are relatively few; most of the variety in cultivation comes from the striking range of natural stem forms across the different species.
Common problems
- Rot — the usual cause of loss, from a heavy, water-retentive mix or standing water; stems yellow, soften and drop.
- Shrivelling — thin, wrinkled stems usually mean underwatering or very low humidity, as these forest cacti are less drought-tolerant than their desert relatives.
- Pests — mealybugs (white fluff where stems join) and scale are the most common; spider mites can appear in hot, dry indoor air.
See also
- Rhipsalis baccifera — the type and most familiar species
- Schlumbergera · Hatiora · Lepismium — related epiphytic cacti
- Soil and potting mix · Watering · Repotting · Propagation — cuttings · Pests and diseases