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Last updated on April 19, 2014 at 13:20 EDT

Cactus

A cactus (plural, cacti or cactuses) is a type of succulent plant belonging to the dicotyledonous flowering plant family, Cactaceae. The Cactaceae has (depending upon the authority) between 24 and 220 genera, with around 90 genera being the most widely accepted count, and with anywhere from 1,500 to 1,800 species. Cacti are recognized natives of the Americas, mostly in desert areas. Some are also rainforest epiphytes, growing on tree branches where, despite the high rainfall, water drains off quickly so that “dry” conditions prevail much of the time.

Cacti are almost exclusively New World plants. This means that they are native only in North America and South America. There is however one exception, Rhipsalis baccifera; this species has a pantropical distribution, occurring in the Old World in tropical Africa, Madagascar and Sri Lanka as well as in tropical America. This plant is thought to be a relatively recent colonist in the Old World (within the last few thousand years), probably carried as seeds in the digestive tracts of migratory birds. Many other cacti have become naturalized to similar environments in other parts of the world after being introduced by man.

Although many other succulent plants exist in the Old World, even a few with spines, they are not cacti because they lack areoles (specialized structures unique to cacti and identify the family).

Cacti are believed to have evolved in the last 30 to 40 million years. Long ago, the Americas were joined to the other continents, but separated due to continental drift. Unique species in the New World must have developed after enough the continents had moved apart. Significant distance between the continents was only achieved around in the last 50 million years. It is assumed this explains why cacti do not occur in Africa; the continents had already separated when cacti evolved.

Like other succulents, cacti are well-adapted to life with little precipitation. The leaves have evolved into spines, which in addition to allowing less water to evaporate than regular leaves, defend the cactus against water-seeking animals. Photosynthesis is carried out by enlarged stems, which also store water. Unlike many other succulents, the stem is the only part of a true cactus where this takes place. Very few members of the family have leaves, and when present these are usually rudimentary and soon fall off; they are typically awl-shaped and only 1-3 mm long. Two genera, Pereskia and Pereskiopsis, do however retain large, non-succulent leaves 5-25 cm long and also non-succulent stems; they are possibly primitive genera, thought to be closely similar to the plants that cacti evolved from.

Cacti come in many varieties in a wide range of shapes and sizes. Some grow to great size. Some cacti produce beautiful flowers, which like spines and branches arise from areoles. Many cactus species are night-blooming, as they are pollinated by nocturnal insects or small animals, principally moths and bats. Cacti range from small and round to pole-like and tall, such as the Saguaro.

A number of cactus species are cultivated for use as houseplants, as well as for ornamental gardens. They often form part of xerophilic (dry) gardens in arid regions. Some cacti bear edible fruit.

Genera

  • Acanthocalycium Backeb.
  • Acanthocereus (Engelm. ex Berger) Britt. & Rose
  • Triangle cactus
  • Acharagma N.P. Taylor
  • Ancistrocactus
  • Aporocactus
  • Ariocarpus Scheidw.
  • Livingrock
  • Armatocereus Backeb.
  • Arrojadoa Britt. & Rose
  • Arthrocereus A. Berger
  • Astrophytum Lem.
  • Austrocactus Britt. & Rose
  • Austrocylindropuntia Backeb.
  • Aztekium Boed.
  • Bergerocactus Britt. & Rose
  • Snakecactus
  • Blossfeldia Werderm.
  • Borzicactus
  • Brachycereus Britt. & Rose
  • Brasilicereus Backeb.
  • Brasilopuntia (Schumann) Berger
  • Browningia Britt. & Rose
  • Buiningia
  • Calymmanthium F.Ritter
  • Carnegiea Britton & Rose
  • Carnegia cactus, Saguaro
  • Cephalocereus Pfeiff.
  • Old man cactus
  • Cephalocleistocactus F. Ritter
  • Cereus P. Mill.
  • sweetpotato cactus
  • Chamaecereus
  • Cintia Riha
  • Cipocereus F.Ritter
  • Cleistocactus Lem.
  • Cochemeia (K. Brandegee) Walton
  • Coleocephalocereus Backeb.
  • Coloradoa
  • Consolea Lemaire
  • Copiapoa Britt. & Rose
  • Corryocactus Britt. & Rose
  • Coryphantha (Engelm.) Lem.
  • Beehive cactus
  • Cumulopuntia F. Ritter
  • Cylindropuntia (Engelmann) F.M. Knuth
  • Dendrocereus Britt. & Rose
  • Denmoza Britt. & Rose
  • Discocactus Pfeiff.
  • Disocactus Lindley.
  • Dolichothele
  • Echinocactus Link & Otto
  • Barrel cactus
  • Echinocereus Engelm.
  • Hedgehog cactus
  • Echinofossulocactus
  • Echinomastus Britt. & Rose
  • Echinopsis Zucc.
  • Encephalocarpus
  • Epiphyllum Haw.
  • Climbing cactus
  • Epithelantha A. Weber ex Britt. & Rose
  • Pingpong ball cactus
  • Eriosyce Phil.
  • Escobaria Britt. & Rose
  • Foxtail cactus, Pincushion cactus
  • Escontria Rose
  • Espostoa Britt. & Rose
  • Espostoopsis Buxbaum
  • Eulychnia Phil.
  • Facheiroa Britt. & Rose
  • Ferocactus Britt. & Rose
  • Barrel cactus
  • Frailea Britt. & Rose
  • Geohintonia Glass & Fitz Maurice
  • Grusonia F. Reichenbach
  • Gymnocalycium Pfeiff.
  • Chin cactus
  • Haageocereus Backeb.
  • Hamatocactus
  • Harrisia Britt.
  • Applecactus
  • Hatiora Britt. & Rose
  • Heliocereus
  • Hildewintera
  • Hylocereus (Berger) Britt. & Rose
  • Nightblooming cactus
  • Islaya
  • Isolatocereus Backeb.
  • Jasminocereus Britt. & Rose
  • Lasiocereus F. Ritter
  • Lemaireocereus
  • Leocereus Britt. & Rose
  • Lepismium
  • Leptocereus (Berger) Britt. & Rose
  • Leuchtenbergia Hooker
  • Lobivia Britt. & Rose
  • Lophocereus
  • Lophophora Coult.
  • Peyote
  • Maihuenia (Philippi ex F.A.C.Weber) K.Schumann
  • Maihueniopsis
  • Mamillopsis
  • Mammillaria Haw.
  • Fishhook cactus, Globe cactus, Pincushion cactus, Bird’s-nest cactus
  • Mammilloydia Buxbaum
  • Matucana Britt. & Rose
  • Melocactus Link & Otto
  • Micranthocereus Backeb.
  • Mila Britt. & Rose
  • Melocactus Link & Otto
  • Myrtillocactus Console
  • Neobesseya
  • Neobuxbaumia Backeb.
  • Neochilenia
  • Neogomesia
  • Neolloydia Britt. & Rose
  • Neoporteria
  • Neoraimondia Britt. & Rose
  • Neowerdermannia Fric
  • Notocactus (K.Schum.) Fric
  • Obregonia Fric
  • Opuntia P. Mill.
  • Prickly pear, Cholla
  • Oreocereus Riccob.
  • Oroya Britt. & Rose
  • Ortegocactus Alex.
  • Pacherocactus G.D. Rowley
  • Pachycereus (Berger) Britt. & Rose
  • Parodia Speg.
  • Pediocactus Britt. & Rose
  • Hedgehog cactus
  • Pelecyphora Ehrenberg
  • Peniocereus (Berger) Britt. & Rose
  • Pereskia P. Miller
  • Pereskiopsis Britt. & Rose
  • Pfeiffera
  • Pilosocereus Byles & Rowley
  • Tree cactus
  • Polaskia Backeberg
  • Praecereus Buxbaum
  • Pseudoacanthocereus F. Ritter
  • Pseudorhipsalis Britt. & Rose
  • Pterocactus K. Schumann
  • Pygmaeocereus H. Johnson & Backeb.
  • Quiabentia Britt. & Rose
  • Rathbunia
  • Rauhocereus Backeberg
  • Rebutia K. Schumann
  • Rhipsalidopsis
  • Rhipsalis Gaertn.
  • Samaipaticereus Cardenas
  • Schlumbergera Lem.
  • Holiday Cactus
  • Sclerocactus Britt. & Rose
  • Fishhook cactus
  • Selenicereus (Berger) Britt. & Rose
  • Moonlight cactus, Night blooming cereus
  • Setiechinopsis Backeb. ex de Haas
  • Stenocereus (Berger) Riccob. Organ pipe cactus and others
  • Stephanocereus A. Berger
  • Stetsonia Britt. & Rose
  • Strombocactus Britt. & Rose
  • Sulcorebutia Backeberg
  • Tacinga Britt. & Rose
  • Tephrocactus Lemaire
  • Thelocactus (K. Schum.) Britt. & Rose
  • Toumeya
  • Trichocereus
  • San Pedro
  • Tunilla D.R. Hunt & Iliff
  • Turbinicarpus Buxbaum & Backeberg
  • Top cactus
  • Uebelmannia Buining
  • Weberbauercereus Backeberg
  • Weberocereus Britt. & Rose
  • Weingartia Werderm.
  • Wigginsia
  • Wilcoxia
  • Wittia
  • Yavia R. Kiesling & J. Piltz
  • Yungasocereus F. Ritter
  • Zygocactus
Cactus