Senita Cactus
Lophocereus schottii
Family: Cactaceae
This is a columnar cactus reaching 10-12’ tall though some individuals reach over 20’. The stems are relatively much thicker and substantial than most columnar cacti. The new grown may often exhibit a reddish or purplish tint, especially in winter—anthocyanin development which protects cells from freezing or decimation from drought. Eventually the tops of older stems will develop what is called a pseudocephalium—the spines become more dense and thick, and this is where the plants flowers will emerge from. Late spring to early summer through these pseudocephaliums flowers emerge which can be reddish, purple, or most commonly white. The flowers are followed by spherical, red fruits that contain red pulp.
Photo of plant in the wild in Peru by doubleaneura on iNaturalist
Pictured below is the monstrose genetic mutation that is popular in cultivation, called the totem pole cactus. This is the same species, except that it has a genetic mutation that causes the stems to look almost like melted candles or as the same implies, a totem pole. The original plants are found in a small area NE of El Arco, about halfway down the Baja peninsula. They are sterile and do not sexually reproduce, but because of the soft gravelly, sandy soil they occur in, stems that break off often re-root and thus clone themselves forming small, restricted populations of this plant. There are most certainly many more plants growing in backyards than there are in the wild. The original cause of this mutation is unknown.
Plant in full to part sun, low water when established—in the summer, a drink once or twice a month, if the plants are in well-drained soils, helps keep plants looking their best. The plants are generally hardy into the mid to lower 20s°F. The tops of the large stems are the most frost-tender part of the plant, while the older, lower parts of the stems are more tolerant of cold.
The senita cactus exhibits mutualism with the senita moth (Upiga virescens). The senita moth is the only nocturnal pollinator of the cactus, and the moth relies on the cactus as a host for reproduction.. Fruits are eaten by birds and other animals.
The Genus, Lophocereus, honors Arthur Schott, a German naturalist and plant collector who surveyed the border between the United States and Mexico. The species, schottii, is named for Arthur Carl Victor Schott (1814-1875) a naturalist on the Mexican Boundary Survey. There are 3 species of Lophocereus in the southwestern United States and Mexico. These plants were formally placed in the genus Pachycereus.
This is of the few columnar cactus species from southern Arizona—occurs on the border in Organ Pipe National Monument south into north-western Mexico, particularly Baja California and Sonora. This species tolerance of ultramafic soils (soils derived from igneous rock with extremely low silica composition, being made of almost all olivine and pyroxene—generally not friendly to plant development) facilitate the endemism of this plant species and are associated with its distribution.
The Totem Pole Cactus (Lophocereus schottii forma monstrosus) This monstrous form is restricted to a small area NE of El Arco, about halfway down the Baja peninsula. The plants are generally sterile. This growth form is found in at least two wild populations in a very soft sandy and gravely soil. In these two locations the plants persist because stem sections break off periodically and root along the sides to produce new plants. Clones of these plants are very popular in cultivation. Photo by terrysamson on iNaturalist
Typical flowering stem of Senita cactus. Photo by spheller on iNaturalist
The fruits, photo by jrebman, iNaturalist