A cactus is a member of the plant family Cactaceae, a family of the order Caryophyllales comprising about 127 genera with some 1,750 known species. 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.
Gymnocalycium, commonly called chin cactus, is a genus of about 70 South American species of cactus. The genus name Gymnocalycium refers to the flower buds bearing no hair or spines. In a 2023 classification of the tribe Cereeae, it was placed as the only genus in the subtribe Gymnocalyciinae, having formerly been placed in the subtribe Rebutiinae.
Cleistocactus is a genus of flowering plants in the cactus family Cactaceae, native to mountainous areas - to 3,000 m (9,843 ft) - of South America. The name comes from the Greek kleistos meaning closed because the flowers hardly open.
Geohintonia mexicana is a species of cacti, the only species in the genus Geohintonia. This genus is named after its discoverer George S. Hinton. As its specific epithet suggests, the plant is found in Mexico, where it grows on gypsum hills near Galeana.
Strombocactus disciformis is a rare species of cacti and the only species of the genus Strombocactus. The plant originates from Central and Northeast Mexico.
The lava cactus is a species of cactus, Brachycereus nesioticus, the sole species of the genus Brachycereus. The plant is a colonizer of lava fields – hence its common name – where it forms spiny clumps up to 60 cm (24 in) tall. Its solitary white or yellowish white flowers open in the daytime. It is endemic to the Galápagos Islands.
Oroya is a genus of cacti, native to Peru. The genus is widespread in the Peruvian Andes.
Reicheocactus is a monotypic genus of cactus in the family Cactaceae, native to north western Argentina. It has only one known species, Reicheocactus famatimensis.
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.
Ferocactus pilosus, also known as Mexican lime cactus or Mexican fire barrel, is a species of cactus in North America.
Soehrensia candicans is a species of cactus from northern and western Argentina. It has large fragrant white flowers that open at night.
Ferocactus gracilis, the fire barrel cactus, is a species of Ferocactus from Northwestern Mexico. This cactus gets its common name from the striking red coloration of its defensive spines and flowers.
Gymnocalycium denudatum is a species of Gymnocalycium from Brazil to Argentina.
Acanthocalycium thionanthum is a species of Acanthocalycium from Argentina.
Oreocereus trollii, commonly known as the Old Man of the Andes cactus, is a species of cacti native to Argentina and Bolivia. Though listed as Least Concern by the IUCN, the plant is collected extensively, and in some areas is threatened.
Lobivia ancistrophora is a species of cactus. It has a globular shape, few spines, with large, white flowers attached to long, green tubes. It occurs in Bolivia, at altitudes of 600–1800 metres. Under its synonym Echinopsis ancistrophora it has gained the Royal Horticultural Society's Award of Garden Merit.
Acanthocalycium klinglerianum is a species of cactus endemic to Bolivia.
Acanthocalycium rhodotrichum is a species of Acanthocalycium found in Argentina, Bolivia, Brazil, Paraguay, and Uruguay.
Pachycereus weberi is a columnar cactus plant native to Mexico.
Acanthocalycium leucanthum is a species of flowering plant in the cactus family Cactaceae from Argentina.
