Rhipsalis, a tropical cactus

This year, in the context 'Green craftsmanship' theme of the Dutch Association of Botanical Gardens, we will introduce you to a series of well-known houseplants that can also be found in the Bush. This edition is about a cactus. When you think of cacti, you picture spiny plants that are adapted to dry, warm areas. But cacti also grow in the tropical rainforest. Often tropical cacti grow in the wild as epiphytes.

Where in the World

The tropical cactus we are introducing to you is the Rhipsalis, a plant genus of which most species occur in Central and South America. Only the Rhipsalis baccifera (typically known as the mistletoe cactus) is also found in Africa and on a few islands in the Indian Ocean. It is the only cactus that grows naturally outside of America. Possibly, migratory birds carried the seeds from the Americas across the ocean thousands of years ago. The genus Rhipsalis has over 35 species, all plants with hanging, green stems.

Air purifying stems

The different species all have slightly different shaped stems. Some are round, others flat and ribbed. Some are bald, others slightly bristly. They are all green. Succulents, such as Rhipsalis have stomata in their green stems. These are the openings where gas exchange takes place in a plant. During the day, these stomata are usually closed, but at night they are open, and the plant absorbs carbon dioxide and emits oxygen. This makes the plant an excellent air purifier in your home because, unlike most plants, mistletoe cactus does not use photosynthesis during the day or consume oxygen at night.

In the jungle, the stems produce many small flowers—white, yellow, orange or red, depending on the species. In the living room, this plant will hardly flower.

Ideal houseplant

The Rhipsalis requires little care, making it an ideal houseplant. The location can be in the sun, but also—and preferably—in the semi-shade. The plant can survive a dark place, but it will hardly grow. The Rhipsalis requires water, but not every week. Wait until the ground feels dry to the touch. The plant does not like wet soil for long periods; the chance of rotting is high. Like all cacti, the Rhipsalis is a slow grower. Additional fertilisation is therefore not often necessary. It is best not to feed at all in autumn and winter. If you do add fertiliser, use cactus and succulent fertiliser. Make sure that the plant has enough room to hang; the stems of some species can grow up to metres in length.

Toxic

The stems of Rhipsalis contain a milky sap, which is mildly toxic and can cause skin irritations. If a stem breaks off, the plant may leak for a while. The floor under the plant may become a little sticky. You can plant a broken stem in the ground; chances are it will develop roots. In the Bush, you can find these jungle cacti high up in the tree on the corner of the main route and the path to the Safari Restaurant.