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Growing Succulents in the Desert Column

(List of Growing Succulents in the Desert columns)

"Selenicereus macdonaldiae : The Champion Cactus Flower" by Mark Dimmitt

Pictures by Mark Dimmitt unless otherwise noted
This article may only be reprinted with the author's permission.

Selenicereus macdonaldiae is one of scores of cactus species with the common name “night-blooming cereus” and “queen of the night”. This species is reputed to have the largest flowers in the cactus family; they spread 13 inches across and a foot and a half long. The huge flower is doubly stunning because it emerges from such scrawny stems. The stems are only about a half inch in diameter, and are studded with sparse spines that are just strong enough to be annoying to handle. The weak stems grow up to four feet a year, branching occasionally. In nature the stems climb trees, clinging by adventitious roots. In cultivation stems need to be tied up to keep the plant manageable. In several years a large tangle of stems will form. The huge flowers appear in several waves over a period of three to four weeks in late May and June. They are rather sparse; even a large plant will produce only two or three in a night. Many delicate white petals are surrounded by a crown of thin yellow sepals. The flowers open at dusk and begin to wilt as soon as the sun hits them the following morning. This species should be grown in filtered sun and protected from frost. Training it against a north- or east-facing house wall under the eaves should be sufficient protection in most years in Tucson. Cuttings root easily and will begin to flower in two or three years. There are several other species of Selenicereus, with flowers ranging from as large as those of S. macdonaldiae to only a few inches wide. Selenicereus grandiflorus flowers are reputed to reach 15 inches across, but mine have not been that large. A couple of the small-flowered species are frost-hardy. Selenicereus (Cryptocereus) anthonyanus has ric-rac stems and the flowers have dark purplish-red sepals that starkly contrast with the white petals.