A cactus is a member of the plant family Cactaceae, a family comprising about 127 genera with some 1,750 known species of the order Caryophyllales. The word cactus derives, through Latin, from the Ancient Greek word κάκτος (káktos), a name originally used by Theophrastus for a spiny plant whose identity is now not certain. Cacti occur in a wide range of shapes and sizes. They are native to the Americas, ranging from Patagonia in the south to parts of western Canada in the north, with the exception of Rhipsalis baccifera, which is also found in Africa and Sri Lanka. Cacti are adapted to live in very dry environments, including the Atacama Desert, one of the driest places on Earth. Because of this, cacti show many adaptations to conserve water. For example, almost all cacti are succulents, meaning they have thickened, fleshy parts adapted to store water. Unlike many other succulents, the stem is the only part of most cacti where this vital process takes place. Most species of cacti have lost true leaves, retaining only spines, which are highly modified leaves. As well as defending against herbivores, spines help prevent water loss by reducing air flow close to the cactus and providing some shade. In the absence of true leaves, cacti's enlarged stems carry out photosynthesis.
In botany, areoles are small light- to dark-colored bumps on cacti out of which grow clusters of spines. Areoles are important diagnostic features of cacti, and identify them as a family distinct from other succulent plants. The spines are not easily detachable, but on certain cacti, members of the subfamily Opuntioideae, smaller, detachable bristles, glochids, also grow out of the areoles and afford additional protection.
Mammillaria is one of the largest genera in the cactus family (Cactaceae), with currently 200 known species and varieties recognized. Most of the mammillaria are native to Mexico, but some come from the southwest United States, the Caribbean, Colombia, Venezuela, Guatemala and Honduras. The common name "pincushion cactus" refers to this and the closely related genus Escobaria.
Pereskia is a small genus of about four species of cacti that do not look much like other types of cacti, having substantial leaves and non-succulent stems. The genus is named after Nicolas-Claude Fabri de Peiresc, a 16th-century French botanist. The genus was more widely circumscribed until molecular phylogenetic studies showed that it was paraphyletic. The majority of species have since been transferred to Leuenbergeria and Rhodocactus. Although Pereskia does not resemble other cacti in its overall morphology, close examination shows spines developing from areoles, and the distinctive floral cup of the cactus family.
In 1984, the International Organization for Succulent Plant Study set up a working party, now called the International Cactaceae Systematics Group, to produce a consensus classification of the cactus family, down to the level of genus. Their classification has been used as the basis for systems published since the mid-1990s. Treatments in the 21st century have generally divided the family into around 125–130 genera and 1,400–1,500 species, which are then arranged in a number of tribes and subfamilies. However, subsequent molecular phylogenetic studies have shown that a very high proportion of the higher taxa are not monophyletic, i.e. they do not contain all of the descendants of a common ancestor. As of August 2023, the internal classification of the family Cactaceae remained uncertain and subject to change. A classification incorporating many of the insights from the molecular studies was produced by Nyffeler and Eggli in 2010.
Pereskiopsis is a genus of cactus in the subfamily Opuntioideae. Unlike typical cacti, it has persistent fleshy leaves. The genus name refers to its resemblance to the genus Pereskia. Most species are found in Mexico south through Guatemala to Honduras, with one species in Bolivia. The incorrect spelling Peireskiopsis has also been used.
Brasiliopuntia is a genus in the cactus family, Cactaceae. It contains only one species, Brasiliopuntia brasiliensis.
Rhodocactus is a genus of flowering plant in the cactus family Cactaceae, native to central South America. Unlike most species of cacti, Rhodocactus has persistent leaves and a fully tree-like habit. The genus was sunk into a broadly circumscribed Pereskia, but molecular phylogenetic studies from 2005 onwards showed that with this circumscription Pereskia was paraphyletic, and in 2016, Rhodocactus was restored for southern South American species.
Yavia cryptocarpa is a species of cactus and the only species of the newly discovered genus Yavia. The genus is named after Argentina's department Yavi, Jujuy Province, where the plant is endemic to sparsely vegetated rocky slopes. The plant is also sometimes put in the tribe Notocacteae. The specific epithet cryptocarpa refers to the plant being a cryptocarp. This means that the fruits are formed inside the plant's body, thus being only visible when the plant shrinks in the drought period.
Selenicereus megalanthus, synonym Hylocereus megalanthus, is a cactus species in the genus Selenicereus that is native to northern South America, where it is known, along with its fruit, by the name of pitahaya. The species is grown commercially for its yellow fruit, but is also an impressive ornamental climbing vine with perhaps the largest flowers of all cacti.
Rhodocactus bahiensis is a species of tree-like cactus that is endemic to the Brazilian state of Bahia. First described as Pereskia bahiensis, it was transferred to Rhodocactus in 2016. Like all species in the genus Rhodocactus, and unlike most cacti, it has persistent leaves. In its native locality, it is used to form hedges.
Rhodocactus stenanthus is a species of cactus that is endemic to Brazil. First described as Pereskia stenantha, it was transferred to Rhodocactus in 2016. Like all species in the genus Rhodocactus, and unlike most cacti, it has persistent leaves. In its native locality, it is sometimes used in hedges.
Trichocereus macrogonus, synonym Echinopsis macrogonus, is a species of cactus found in Ecuador, Peru and Bolivia. Two varieties are accepted as of September 2023: var. macrogonus and var. pachanoi. Plants contain varying amounts of the psychoactive alkaloid mescaline. They have been used both ritually and intraditional medicine from pre-Columbian times. Trichocereus macrogonus is one of a number of similar species that may be called San Pedro cactus. Indigenous names include achuma and huachuma, although these too may be applied to similar species.
Opuntia fragilis, known by the common names brittle pricklypear and little prickly pear, is a prickly pear cactus native to much of western North America as well as some midwestern states such as Illinois, Iowa, Wisconsin and Michigan. It also occurs in several Canadian provinces. It is known from farther north than any other cactus, occurring at as far as 56°N latitude in British Columbia. There is an isolated and possibly genetically unique population in Eastern Ontario known as the "Kaladar population".
Cylindropuntia californica is a species of cholla cactus known by the common name snake cholla. It is primarily found in Baja California, Mexico and the southernmost part of California in the United States. It is characterized by a short, decumbent habit, yellow-green flowers, elongated stems, and short spines. It is mostly found in coastal sage scrub and coastal chaparral habitats, but two varieties in Baja California can be found in foothills and deserts. In California, variety californica is regarded as a rare and threatened plant, with a California Native Plant Society listing of 1B.1, in part due to its limited number of occurrences and threats from development. It formerly was considered to have a larger range due to the inclusion of Cylindropuntia bernardina within it as the variety parkeri.
Pereskia aculeata is a scrambling shrub in the family Cactaceae. Common names include Barbados gooseberry, blade-apple cactus, leaf cactus, rose cactus, and lemonvine. It is native to tropical America. The leaves and fruits are edible, containing high quantities of protein, iron and other nutrients, and it is a popular vegetable in parts of the Brazilian state of Minas Gerais under the name of ora-pro-nóbis.
Leuenbergeria bleo, formerly Pereskia bleo, is a leafy cactus, native to the shady, moist forests of Central America, that grows to a woody, prickly shrub about 2 m tall with large, orange flowers resembling rose blossoms.
Leuenbergeria is a genus of flowering plant in the family Cactaceae, mostly native around the Caribbean. Unlike most cacti, it has persistent leaves and develops bark on its stems early in its growth. The genus was created in 2012 by Joël Lodé. Before the creation of Leuenbergeria as a genus, the species within it were included in a broadly circumscribed genus, Pereskia. Leuenbergeria is the only genus in the subfamily Leuenbergerioideae.
Rhodocactus nemorosus is a species of flowering plant in the cactus family Cactaceae, native to southern Brazil, Paraguay, Uruguay and northeast Argentina. Like all species in the genus Rhodocactus and unlike most cacti, it has persistent leaves. It was first described by Nicolás Rojas Acosta in 1897 as Pereskia nemorosa, and transferred to Rhodocactus in 2016.
Rhodocactus sacharosa, synonym Pereskia sacharosa, is a species of flowering plant in the cactus family Cactaceae, native from Bolivia and west-central Brazil to Paraguay and northern Argentina. Like all species in the genus Rhodocactus and unlike most cacti, it has persistent leaves. It was first described in 1879.
