Pfeiffera monacantha (Griseb.) P.V. Heath
Acanthorhipsalis monacantha, Rhipsalis monacantha, Lepismium monacanthum,
This species is native to northwestern Argentina and southeastern Bolivia. It grows as an epiphyte or lithophyte at elevations from 980 to 6,560 feet (300 to 2,000 m).
Pfeiffera monacantha, also known as Lepismium monacanthum or Rhipsalis monacantha, is a slow-growing shrubby cactus with flat to three-angled branches with serrated ribs and felted areoles with a few bristles and 1 to 6 spines. The branches are up to 18 inches (45 cm) long and 1.2 inches (3 cm) wide, at first erect, becoming pendent as they grow. Spines are stout, black, and up to 0.4 inches (1 cm) long. Flowers are waxy orange, up to 0.6 inches (1.5 cm) long, up to 0.8 inches (2 cm) in diameter, and appear solitary at areoles. Fruits are small, spherical, orange or pale pink, more or less translucent, and decorate the plant for months.
USDA hardiness zones 10a to 11b: from 30 °F (−1.1 °C) to 50 °F (+10 °C).
How to Grow and Care
Rhipsalis do not thrive in direct sunlight. Exposure to the afternoon sun can burn the leaves, turn them yellow or lead to spotting. However, they will not bloom without sufficient sunlight, and their growth can be stunted. Therefore, these cacti do best with morning sun and full shade in the afternoon.
As Rhipsalis is commonly grown indoors, care must be given to the placement of the plants. They should be kept at least 20 inches (50 cm) from windows that receive midday or afternoon sun. The glass in the windows can multiply the heat from the sun's rays, causing sunburned leaves. Keep in mind that in its native environment, Rhipsalis is accustomed to receiving light filtered through dense, overhanging tree branches. Picturing this environment can help you adjust your lighting accordingly.
Rhipsalis is not a drought-resistant plant, so regular watering is essential. Overwatering, however, can cause weak stems and rotted roots. Using a watering can help you measure the amount of water you are providing. The pot size, compared to the size of the plant, the humidity levels in the home, and the type of potting soil used can all affect the watering frequency.
Learn more at How to Grow and Care for Rhipsalis.
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