What is Cereus?

Cereus is a term for various types of cacti that have elongated segments. Many different types of cacti employ this term in their botanical names, such as Hylocereus and Selenicereus. There is also a genus called Cereus. All of these types of cacti have at least one species with large flowers that bloom at night, and are known as night-blooming cereus. Another species with this common name is a type of tropical, jungle-dwelling cactus known as Epiphyllum oxypetalum.

The terminology and growth habits of night-blooming cereus plants are quite confusing, since so many types of cacti have this name. Also, the growth habits and horticultural requirements of the plants vary quite widely. Some of the plants come from radically different backgrounds, ranging from the hot and dry Sonoran deserts to the moist environments of trees in tropical jungles. All of these types of cacti can be grown as houseplants or outside in warmer climates. Often, they are grown outside during the growing season and brought indoors during cool winters.

The cactus that is commonly thought of as the night-blooming cereus is a species of orchid cacti, the Epiphyllum. These cacti are atypical in that they live on trees in the jungle and prefer rich soil that drains well, along with humid environments. The stems are about 2 feet long (.60 m) and thin with scalloped edges. There are a very large number of hybrids of Epiphyllum, with flowers in a large array of colors.

Epiphyllum oxypetalum is the species of orchid cactus that blooms at night. There are also a number of hybrids of this species. They prefer to be kept somewhat dry in the winter and usually bloom in the spring, with flowers that can be up to 10 inches (25 cm) wide. The plants produce more flowers when they have been exposed to cool temperatures, but must be prevented from freezing. Some hybrids bloom in the winter.

Cereus peruvianus is a tall, columnar cactus that grows to 10 feet (3 m) tall and can spread to 15 feet (4.5 m) wide in arid regions. It produces branches from the bottom of the plant that are ribbed. Its nocturnal flowers are white and 5 inches (12.5 cm) in diameter. If pollinated, large, edible red fruit are sometimes produced. This fruit has been the subject of research to determine their suitability as a crop for the deserts of Israel.

This species of cactus grows best in full sun. It can tolerate periods of drought, but should be watered occasionally during dry summers. Like most cacti, it should be kept dry in the winter. Water should never be left standing under the plant.

Another species commonly known as night-blooming cereus is Hylocereus undatus, which produces white flowers 12 inches (30 cm) or more wide, that often resemble those of magnolias. Older plants will produce a number of flowers every two weeks from late summer throughout the fall. Sometimes edible fruit are produced near the end of the flowering season.

This plant is native to South America. It can become a large vine if grown outside in warm areas, reaching up to 40 feet (12 m) long. The plants require some direct sun and soil that is well-drained. An equal mix of potting soil and sand is generally recommended as a planting mixture.

If grown in an area prone to frost, this type of cactus should be grown indoors over the winter. If grown as houseplants, they must be kept in the dark entirely from sunset to sunrise between July to October. Hylocereus houseplants should not be watered more than once a week, and then only if dry. These cacti can grow vigorously inside also, but can be cut back without causing damage to the plants.

Selenicereus grandiflora is another type of night-blooming cereus that grows on trees in the wild. It is easily grown in full sun. This plant blooms earlier in the year than the other species, and only blooms once per year at most. Often, plants grown as this species have been misidentified and, in reality, are other types of cacti.