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.
Arrojadoa is a genus of cacti, comprising 6 species and several varieties. It is named after the Brazilian botanist Miguel Arrojado Lisboa (1872–1932) who was superintendent of the Brazilian Railways at the time that Britton and Rose described the genus in 1920. The genus occurs only in northern Brazil and is found at rocky places, under shrubs, which support their frail stalk. They are subtropical plants, with very little frost tolerance.
Pachycereus is a genus of large cacti native to Central America and Mexico. They form large shrubs or small trees up to 15 m tall, with stout stems up to 1 m in diameter. Pachycereus comes from the ancient Greek παχύς (pachys) meaning "thick" and the Latin cereus meaning "torch".
Cephalocereus senilis, the old man cactus, is a species of cactus native to Hidalgo and Veracruz in central Mexico. It is threatened in the wild, but widespread propagation and popularity in cultivation have reduced the demand on wild populations.
Ariocarpus is a small genus of succulent, subtropical plants of the family Cactaceae.
Thelocactus is a genus of flowering plants in the cactus family Cactaceae. Members of the genus are native to the arid lands of Central and Northern Mexico.
The term ceroid cactus is used to describe any of the species of cacti with very elongated bodies, including columnar growth cacti and epiphytic cacti. The name is from the Latin cēreus, meaning "wax taper ", referring to the stiff, upright form of the columnar species. Some species of ceroid cacti were known as torch cactus or torch-thistle, supposedly due to their use as torches by Native Americans in the past.
Selenicereus, sometimes known as moonlight cactus, is a genus of epiphytic, lithophytic, and terrestrial cacti, found in Mexico, Central America, the Caribbean and northern South America. The term night-blooming cereus is also sometimes used, but this is also used for many night-blooming cacti, including Epiphyllum and Peniocereus. In 2017, the genus Hylocereus was brought into synonymy with Selenicereus. A number of species of Selenicereus produce fruit that is eaten. The fruit, known as pitaya or pitahaya in Spanish or as dragon fruit, may be collected from the wild or the plants may be cultivated.
Cephalocereus is a genus of slow-growing, columnar-shaped, blue-green cacti. The genus is native to Mexico.
Leocereus is a genus of cactus. Its only species is Leocereus bahiensis, first described by Nathaniel Lord Britton and Joseph Nelson Rose in 1926.
Oreocereus is a genus of cacti, known only from high altitudes of the Andes. Its name means "mountain cereus", formed from the Greek prefix oreo- and the Neo-Latin cereus, meaning wax or torch.
Mila caespitosa is a species of cacti and the only species of the genus Mila. Its generic name is an anagram of Lima, Peru, the city near which the plant is found. The genus was first thought to comprise 13 species, until recent studies suggest they form one very variable species.
Grusonia is a genus of opuntioid cacti, originating from the North American Deserts in Southwest United States and northern Mexico, including Baja California. Authors differ on precise boundaries of the genus, which has been included in Cylindropuntia. Corynopuntia, also known as club chollas, is now a synonym, with the genus originally being described by Knuth in 1935. Molecular phylogenetic studies suggest that it should be included in Grusonia, a view accepted by Plants of the World Online as of June 2021.
Selenicereus undatus, the white-fleshed pitahaya, is a species of the genus Selenicereus in the family Cactaceae and is the most cultivated species in the genus. It is used both as an ornamental vine and as a fruit crop - the pitahaya or dragon fruit.
Kroenleinia grusonii, popularly known as the golden barrel cactus, golden ball, "mother-in-law's cushion" or "mother-in-law’s chair", is a species of barrel cactus which is endemic to east-central Mexico.
Mammillaria spinosissima, also known as the spiny pincushion cactus, is a species of flowering plant in the cactus family Cactaceae, endemic to the central Mexican states of Guerrero and Morelos, where they grow at elevations of approximately 1,600 to 1,900 metres. The species was described in 1838 by James Forbes, gardener of the Duke of Bedford. Botanist David Hunt collected a specimen in 1971, when he located one near Sierra de Tepoztlan, Mexico.
Pelecyphora sneedii is a rare species of cactus known by the common names Sneed's pincushion cactus and carpet foxtail cactus. It is endemic to the Chihuahuan Desert of the southwestern United States and northwestern Mexico. It is a small, variable cactus with a lengthy taxonomic history, and is often subdivided into a number of subspecies or varieties. It is usually found on steep, rocky habitats, primarily of limestone geology, in desert scrub or coniferous forest. A species of conservation concern, P. sneedii faces threats from poaching, urban encroachment, and wildfires.
Cereus ( "serious") is a genus of cacti including around 33 species of large columnar cacti from South America. The name is derived from Greek (κηρός) and Latin words meaning "wax", "torch" or "candle". Cereus was one of the first cactus genera to be described; the circumscription varies depending on the authority. The term "cereus" is also sometimes used for a ceroid cactus, any cactus with a very elongated body, including columnar growth cacti and epiphytic cacti.
Espostoa lanata is a species of cactus of the genus Espostoa.
Cephalocereus polylophus is a species of cactus endemic to Mexico. Often grown under the synonym Neobuxbaumia polylopha, it is popular with cactus growers and reproduces well in cultivation.
