A cactus is a member of the plant family Cactaceae, a family comprising about 127 genera with some 1750 known species of the order Caryophyllales. The word "cactus" derives, through Latin, from the Ancient Greek κάκτος, kaktos, 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. Most cacti live in habitats subject to at least some drought. Many live in extremely dry environments, even being found in the Atacama Desert, one of the driest places on earth. Cacti show many adaptations to conserve water. 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 leaves, enlarged stems carry out photosynthesis. Cacti are native to the Americas, ranging from Patagonia in the south to parts of western Canada in the north—except for Rhipsalis baccifera, which also grows in Africa and Sri Lanka.
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.
Curt Backeberg was a German horticulturist especially known for the collection and classification of cacti.
Pereskia, as traditionally circumscribed, is a genus of 17 tropical species and varieties of cacti that do not look much like other types of cacti, having substantial leaves and thin stems. They originate from the region between Brazil and Mexico. Members of this genus are usually referred to as lemon vines, rose cacti or leaf cacti, though the latter also refers to the genus Epiphyllum. The genus is named after Nicolas-Claude Fabri de Peiresc, a 16th-century French botanist.
Didiereaceae is a family of flowering plants found in continental Africa and Madagascar. It contains 20 species classified in three subfamilies and six genera. Species of the family are succulent plants, growing in sub-arid to arid habitats. Several are known as ornamental plants in specialist succulent collections. The subfamily Didiereoideae is endemic to the southwest of Madagascar, where the species are characteristic elements of the spiny thickets.
Armatocereus is a genus of mostly tree-like cacti from South America. These species have a conspicuous constriction at the end of the annual growth. The flowers are mostly white, with a more or less spiny ovary. The fruits are mostly spiny.
Hylocereus is a former genus of epiphytic cacti, often referred to as night-blooming cactus. Several species previously placed in the genus have large edible fruits, which are known as pitayas, pitahayas or dragonfruits. In 2017, a molecular phylogenetic study in 2017 confirmed an earlier finding that the genus Hylocereus was nested within Selenicereus, so all the species of Hylocereus were transferred to Selenicereus.
Blossfeldia is a genus of cactus containing only one species, Blossfeldia liliputiana, native to South America in northwestern Argentina and southern Bolivia. It grows at 1,200–3,500 m altitude in the Andes, typically growing in rock crevices, and often close to waterfalls.
Copiapoa is a genus of flowering plants in the cactus family Cactaceae, from the dry coastal deserts, particularly the Atacama Desert, of northern Chile. It comprises 32 morphologically defined species and 5 heterotypic subspecies. These species vary in form from spherical to slightly columnar and in color from a brownish to blue-green body. They have warty ribs and spiny areoles, and they usually produce tubular yellow flowers which grow from woolly crowns in summer.
Parodia is a genus of flowering plants in the cactus family Cactaceae, native to the uplands of Argentina, Peru, Bolivia, Brazil, Colombia and Uruguay. This genus has about 50 species, many of which have been transferred from Eriocactus, Notocactus and Wigginsia. They range from small globose plants to 1 m (3 ft) tall columnar cacti. All are deeply ribbed and spiny, with single flowers at or near the crown. Some species produce offsets at the base. They are popular in cultivation, but must be grown indoors where temperatures fall below 10 °C (50 °F).
Rhipsalis is a genus of epiphytic flowering plants in the cactus family, typically known as mistletoe cacti. They are found in parts of Central America, the Caribbean and northern regions of South America. They also inhabit isolated locations in Africa and Asia, and are the only cactus group naturally occurring in the Old World. This is the largest and most widely distributed genus of epiphytic cacti.
Hatiora is a small genus of epiphytic cacti which belongs to the tribe Rhipsalideae within the subfamily Cactoideae of the Cactaceae. Recent taxonomic studies have led to the three species formerly placed in subgenus Rhipsalidopsis being removed from the genus, including the well known and widely cultivated ornamental plants known as Easter cactus or Whitsun cactus.
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 New Latin cereus, meaning wax or torch.
Cylindropuntia is a genus of cacti, containing species commonly known as chollas, native to northern Mexico and the Southwestern United States. They are known for their barbed spines that tenaciously attach to skin, fur, and clothing. Stands of cholla are called cholla gardens. Individuals within these colonies often exhibit the same DNA, as they were formerly tubercles of an original plant.
Opuntioideae is a subfamily of the cactus family, Cactaceae. It contains 15 genera divided into five tribes. The subfamily encompasses roughly 220-250 species, and is geographically distributed throughout the New World from Canada, to Argentina. Members of this subfamily have diverse habits, including small geophytes, hemispherical cushions, shrubs, trees, and columnar cacti consisting of indeterminate branches or determinate terete or spherical segments.
In botany, succulent plants, also known as succulents, are plants with parts that are thickened, fleshy, and engorged, usually to retain water in arid climates or soil conditions. It is a characteristic that is not used scientifically for the definition of most families and genera of plants because it often can be used as an accurate characteristic only at the single species level. The word succulent comes from the Latin word sucus, meaning 'juice', or 'sap'. Succulent plants may store water in various structures, such as leaves and stems. Some definitions also include roots, thus geophytes that survive unfavorable periods by dying back to underground storage organs may be regarded as succulents. In horticultural use, the term succulent is sometimes used in a way that excludes plants that botanists would regard as succulents, such as cacti. Succulents are often grown as ornamental plants because of their striking and unusual appearance, as well as their ability to thrive with relatively minimal care.
Maihuenia poepigii, commonly known in Chile as maihuén or hierba del guanaco, is a succulent cactus shrub native to Chile and Argentina. M. poepigii is remarkably tolerant to moisture and cold temperatures.
Schlumbergera gaertneri, formerly Hatiora gaertneri, is a species of epiphytic cactus which belongs to the tribe Rhipsalideae within the subfamily Cactoideae of the Cactaceae. Together with the hybrid with S. rosea, Schlumbergera × graeseri, it is known as Easter cactus or Whitsun cactus and is a widely cultivated ornamental plant. It has received the Royal Horticultural Society's Award of Garden Merit.
The Hylocereeae are a tribe of cacti. Most are found in the tropical forests of Central and northern South America, and are climbers or epiphytes, unlike most cacti. The tribe includes between six and eight genera in different circumscriptions. The plants known as "epiphyllum hybrids" or "epiphyllums", widely grown for their flowers, are hybrids of species within this tribe, particularly Disocactus, Pseudorhipsalis and Selenicereus, less often Epiphyllum, in spite of the common name.
Echinopsis eyriesii is a species of cacti of the genus Echinopsis.
