When you think of air plants, cactus doesn’t come to mind -- till now

A tropical garden never seems complete without a few epiphytes (air plants) growing up in the trees. One of the most interesting but often neglected groups of epiphytes to cultivate are those found in the cactus family. Usually you think of giant saguaros and barrel cactus in the desert as being representative of the cactus family, but this is certainly not the case.

While most cactus are terrestrial, there are a number of species that grow as epiphytes or hemi-epiphytes. Epiphytes are plants that grow on top of other plants and have no roots in the ground. Hemi-epiphytes can either start in the ground and climb into a tree or start in a tree and eventually root in the ground. None of the epiphytes mentioned here are parasites; they hold onto the tree for support only.

All cactus are confined to the New World with one exception, Rhipsalis baccifera. This is an attractive epiphytic species with small fruit that may have been carried to the Old World in the digestive tracts of migratory birds. Another epiphytic species is Hylocereus undatus, better known as Pitaya (actually the common name given to many species of fruit-bearing epiphytic cactus). This particular species is probably native to Mexico and Central America but is now grown around the world for its delicious fruit. Both the plant and fruit are known as Pitaya.

If, while traveling in a tropical country, you’ve found on your breakfast plate a large, round, smooth-skinned red fruit with whitish pulp filled with small black seeds, it’s likely from an epiphytic cactus, and it’s delicious. Other species of these tree-dwelling cactus have skin and pulp of various colors, leading to a wide choice of tasty and visually appealing fruits.

The cultivated Pitaya have no spines or glochids on their fruit, which makes them much easier to handle and eat. Glochids are modified spines, tiny hairs that have the qualities of fiberglass. You don’t feel them at first touch, but will become annoyed by them real quick. Many species of cactus have glochids instead of the typically hard, blood-letting spines.

Here in South Florida, Pitaya (or as the old-timers call it, night-blooming cereus) was once fairly common on many residential properties. My old house had a huge live oak that hosted an immense amount of this thin, spiny cactus up to about 40 feet. Sometimes I would come home late at night and be greeted by the spectacle of hundreds of open, dinner-plate-size flowers and a delightful fragrance. All the flowers would wilt at daybreak, and they only last a single night. Cactus bloom mostly at night to take advantage of nocturnal pollinators, and that is certainly the best time to appreciate their striking flowers.

Pitaya can eventually grow into a large and heavy mass in the canopy of a tree. The live oak at my house blew down in Hurricane Andrew and I’m sure the great amount of extra weight from the cactus contributed to its demise. While a small amount of cactus should not be a problem, I’ve seen branches of various tree species fail under a mass of cactus. Depending on the tree and branch structure, it’s a good idea to periodically remove some of the excess weight of any epiphyte when it gets too big.

All of the epiphytic or hemiepiphytic cactus I’m familiar with are easily propagated from cuttings. You can either use an entire stem segment or a section of a few inches. Whenever I’ve propagated cactus, I let the cutting dry for a few days in a shady spot. I prefer to lay the stems flat on the soil, making sure the nodes (where the spines come out or would come out) are in contact with the soil. This is usually where the roots grow out.

I use a soil mix with coarse sand and a small bit of compost. But I don’t use peat moss in the soil mix because it eventually breaks down and will hold too much moisture for the cactus, which require excellent drainage. If you’re going to keep them in containers or grow them in the ground, make sure the roots never have to tolerate saturated soil.

Some species are loaded with spines (Pitaya) while others are not. The cactus with brightly colored flowers, which we commonly see during the holidays, are hybrids of Schlumbergera species and have no spines. These species are very easy to propagate -- but remember, be careful with the water! They seem to rot overnight when kept too wet.

By the way, you may have noticed that I only used the word “cactus” in this article. Even though the Latin plural of cactus is cacti, I prefer to use the uninflected plural cactus, which is also correctly used in English.

Jeff Shimonski is an ISA-certified municipal arborist, director of horticulture at Jungle Island, and principal of Tropical Designs of Florida. Contact him at This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

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