The Physical Description of a Night Blooming Cereus

Diversity

• Initially, botanists used the genus Cereus to place many new cactus species from the New World. It became a large, all-encompassing genus. As scientific methodologies and taxonomic insight improved, species with common characteristics were pulled from Cereus and grouped into new genera. Night-blooming flowers occur in the genera Hylocereus and Selenicereus, as well as the roughly 25 species that remain in Cereus. All of these cacti may be colloquially referred to as night-blooming cereus. Any plant in the Selenicereus, from the Caribbean, may be also called "queen of the night."

Distinguishing Features

• Cacti in the Cereus genus grow in soil and develop stems that have three to 14 thick stem ribs. Areoles -- rounded clusters of spines in a raised or pitlike bump -- occur on the ribs with thick spines. Hylocereus cacti are epiphytes, which grow on other plants, such as rooting in the branch crotches or bark of trees. These cacti have obvious aerial roots and stems with only three ribs, often with scalloped edges. Areoles are few and short. Those in Selenicereus are epiphytes or lithophytes, growing on or in between rocks. Areoles are short and hairy with few spines atop variably numbered ribs, although a few species have flattened or angled stems. Not all plants have aerial roots.

Flowers

• The vast majority of all the night-blooming cereus plants in genera Cereus, Hylocereus and Selenicereus all produce their flowers at night during the summer. The large flowers in Cereus are more cup- or funnel-shaped compared to the more trumpetlike flowers in Hylocereus and Selenicereus, according to the American Horticultural Society's "A-Z Encyclopedia of Garden Plants." All of them bear variably fragrant flowers that are often cream or white, but some species' blooms are red, pink or coral. Following pollination at night, the flowers become rounded or oval fruits containing shiny black seeds.

Other Insight

• For precise identification, take photographs or the night-blooming cereus plant to a cactus specialist or university botany department. Microscopes and plant keys will help in the process of identifying which genus the plant belongs, as well as its species. Some cultural characteristics may reveal the plant's identity, but isn't an absolute guide. For example, Cereus cacti tolerate light frosts without damage, unlike Hylocereus and Selenicereus plants. Cerus and Hylocereus plants also prosper in acidic conditions for their roots; Selenicereus is best in non-acidic conditions around the roots.