Selenicereus (2004)

By Janet Kister (March 2004)

Selenicereus is one of the four genera of cacti which include night-blooming varieties. The other night-blooming genera are Epiphyllum, Hylocereus and Weberocereus.

The name selenicereus comes from the Greek moon goddess, Selene. Species of Selenicereus are called “moon cacti,” since their flowers open at night.

Members of this family are climbing epiphytes whose flowers can measure up to 16 inches in diameter. These cacti have aerial roots and long, sometimes straggly stems with two to 12 ribs or wings. Their aeroles have short hairs and fine spines which are mostly benign, although some spines can be needlelike.

Selenicereus can grow very large as they clamber over or up trees, plants or rocks. They range in size from 3 to 26 feet in length.

Some species like full sun, but most prefer partial shade. Selenicereus grow in seasonal or rain forest habitat in Texas south through Mexico and into the Caribbean and Cuba. They supposedly also range as far south as Argentina in South America.

In The Cactus Family by Edward Anderson, 28 species of Selenicereus are described. There are a wide variety of stem shapes, some almost leaflike with their wings. The flowers are like those of epiphyllums and occur in spring and summer. They are large, usually fragrant and normally white or cream-colored, although some have yellow, orange, pink or red outer petals.

Selenicereus need warmth and lots of moisture in the spring and summer. A 60- to 85-degree F temperature range is ideal for summer, while 50 to 65 degrees is good for winter. The plants need to be kept somewhat dry in winter.

Since these cacti are tropical, they need a soil such as orchid mix or soil with two parts peat moss, one part regular potting soil and one part sand. Liquid tomato fertilizer is recommended by one source. Selenicereus can be propagated by stem cuttings in spring or summer.

These plants need something to grow on, such as a greenhouse wall, trellis or some other form of support that allows them to grow and flower. In fact one species, S. hamatus, is grown as a living fence in Mexico. Apparently its prominent spurs and hooked tubercules beneath the aeroles make a nice barrier to both humans and animals.

Some Selenicereus species have edible fruits that are harvested for food in South America. The most common of these, S. grandiflorus, is cultivated by the pharmaceutical industry as a source for a substance similar to digitalis used to treat heart problems. This plant, also known as Queen of the Night, has giant blossoms said to smell like vanilla.

Another cultivated species is S. pteranthus, which has blue-green to purplish stems and fragrant, partly purple flowers. The stems are fairly flexible and can be easily trained around a trellis when young. This selenicereus should flower after three to five years when the stems are 2 to 3 feet long.

S. testudo is the plant I am growing and hope to have flowers one day. It occurs in Mexico and, from the photograph I located, should have white blooms with 6-inch-wide flowers and floral tubes with expanded throats up to 10 inches long.

My feeling is that getting these plants to bloom in cultivation may be difficult. If you have success with these cacti, I would love to hear about your experiences.