The plants vary from small, round globes to epiphytes, vines, and large treelike forms. The reduced leaf surface, the enlarged fleshy stem, which is well fitted to store water and to retain it, and the ramified and extensive root system (much reduced in cultivated cacti) make the plant particularly adapted to regions of high temperature and long dry periods. Cacti are not restricted to desert regions, however, for in America they range from the tropics into Canada.
Most cacti bloom in the spring for a very short period, sometimes for only a few hours. The blossoms are noticeably sensitive to light, and often different species blossom only at specific times of the day. One of the most famous of the cacti is the night-blooming cereus usually classified as Selenicereus or C. grandiflora (several other night-blooming cactus species bear the same common name). Its fragrant blossoms unfold at a visible rate after sunset and last only a single night. In many of its native habitats the flowering of this cactus is celebrated with festivals.
Economic Importance
The largest cactus genus is Opuntia, jointed-stemmed species recognizable by the fleshy stems made up of either cylindrical (in the cane cacti and the chollas) or flattened (in the prickly pears) joints called pads. The large pear-shaped berries of several of these species are edible, e.g., the cultivated varieties of the Indian fig and the tuna. This fruit is common in Mexican markets; the plants have been widely naturalized in the Mediterranean countries, Australia, and elsewhere as a source of food. Most opuntias grow so rapidly to a large and ungainly size that they are unsuitable for cultivation as ornamentals, and in the wild often become weeds.
However, the major economic importance of the cactus family is in the florists' trade. Among those cultivated for their showy blossoms are the Christmas cactus (Zygocactus) and species of Echinocereus and of Epiphyllum, the orchid cactus. The pincushion cacti (Mammillaria), the golden ball cactus (Echinocactus), and the hedgehog cactus (Echinopsis) are among the many grown as oddities for their curious appearance.
The nopal (Nopalea coccinellifera) is the cactus traditionally cultivated as a host for the cochineal insect, and the hallucinatory drug mescaline occurs in the genera Lophophora (peyote) and Trichocereus. Other cacti are used as a substitute for wood, as stock feed, and for hedges.
Classification
Cactus is classified in the division Magnoliophyta, class Magnoliopsida, order Caryophyllales, family Cactaceae.
Bibliography
See L. Benson, The Cacti of the United States and Canada (1982) and A. C. Gibson and P. S. Nobel, The Cactus Primer (1986).
Licensed from Columbia University Press
Licensed from Columbia University Press
Golden rainbow cactus (Echinocereus dasyacanthus), a hedgehog cactus, growing in the desert elipsis
Learn more about cactus with a free trial on Britannica.com.
National monument, southwestern Arizona, U.S., at the Mexican border. It was established in 1937. With an area of 330,689 acres (133,929 hectares), it preserves segments of the mountainous Sonoran Desert and is named for the organ-pipe cactus. Wildlife includes Gila monsters, antelope, coyotes, and a variety of birds.
Learn more about Organ Pipe Cactus National Monument with a free trial on Britannica.com.
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