The Rare Cactus Encyclopedia

In-depth profiles, care guides, and rarity rankings for every genus we cover.

Cactus types are easiest to tell apart by growth form: flat geophytes like the living rock cactus and peyote, eight-ribbed star cactus, columnar torches like San Pedro, globular pincushions, and banded hedgehogs like the rainbow cactus. At rarecactus.com we grow all 25 genera below from seed and key each against Kew POWO.

Browse by genus

Each genus page includes species profiles, care guides, and a complete taxa listing.

Ariocarpus

Living Rocks

Slow-growing, flat-bodied masterpieces of the Chihuahuan Desert. Among the most sought-after collector cacti in existence.

Lophophora

A Button-Like Cactus

The best-known species, Lophophora williamsii, grows in the Chihuahuan Desert along the Texas–Mexico border, tucked into desert scrub on limestone hillsides.

Copiapoa

Atacama Giants

Native to the driest non-polar desert on Earth. Slow, architectural, and increasingly rare due to habitat destruction.

Mammillaria

Pincushion Cacti

The largest cactus genus, but select rare species remain almost unknown in cultivation. A genus with surprising depth.

Astrophytum

Star Cacti

Geometric perfection. Rare cultivars and Japanese hybrids command serious collector prices. Deeply satisfying to grow.

Echinocereus

Hedgehog Cacti

Bold lateral flowers in scarlet, magenta, and green. Range spans US prairie to Mexican highland; many species are exceptionally cold-hardy.

Echinopsis

Trichocereus, San Pedro

Spectacular nocturnal blooms and rare forms including cristate and monstrose mutations. Serious collector depth.

Turbinicarpus

Turbo Cacti

Tiny, threatened, and extraordinarily beautiful. Many species are critically endangered in their native San Luis Potosi.

Aztekium

Stone Flowers

Only three species exist. Grows on near-vertical gypsum cliffs. The rarest cultivated cactus genus in the world.

Ferocactus

Barrel Cacti

Bold, architectural barrels with spectacular spine forms. Certain species offer genuine collector appeal and striking presence.

Gymnocalycium

Chin Cacti

South American gems with subtle beauty. Rare forms include stunning variegates and colour mutations prized by collectors.

Lithops

Living Stones

Mesemb stone-mimics from South Africa and Namibia; winter-growers with translucent windows and autumn flowers from a fissure between paired leaves.

Pseudolithos

False Stone

Known for their unusual stone-like or pebble appearance. These plants originate from the arid regions of East Africa and the Arabian Peninsula.

Epithelantha

Button Cacti

Chalk-white miniature buttons of the Chihuahuan Desert; ten POWO species completely covered in densely appressed pectinate spines, several confined to single limestone outcrops.

Coryphantha

Helmet-Flower Cacti

Big-tubercled Mexican mountain cacti with large yellow or rose-magenta flowers from the apex. Includes the genus’s only CITES Appendix I plant, a Coahuila microendemic.

Pelecyphora

Woodlouse & Pinecone Cacti

Tiny limestone-obligate Chihuahuan miniatures with paired pectinate or imbricate tubercles; entire genus on CITES Appendix I since 1975. The 2022 PhytoKeys consolidation absorbed Encephalocarpus.

Obregonia

Artichoke Cactus

Monotypic Tamaulipan-valley microendemic with a flat artichoke-mimic rosette of overlapping triangular tubercles; CITES Appendix I, named for Mexican President Obregón.

Strombocactus

Disc Cacti

Lithophytic disc-shaped cacti hanging on near-vertical Mexican calcareous-shale walls; entire genus on CITES Appendix I. The 13:8 Fibonacci spiral tubercles of S. disciformis are iconic.

Geohintonia

Sister to Aztekium

Monotypic gypsum-cliff microendemic from a single Galeana NL site; co-described with Aztekium hintonii in 1992. Rejects limestone in cultivation despite the gypsum habitat.

Leuchtenbergia

Agave Cactus

Monotypic central-Mexican calcicole with the most agave-like silhouette in Cactaceae; long pencil tubercles tipped with flexible papery spines, large yellow flowers from the apex.

Acharagma

Groove-less Buttons

Three Coahuilan limestone microendemics defined by smooth ungrooved tubercles. Intensely collected for their rarity, miniature scale, and precise locality data.

Cochemiea

Baja Hook Cacti

Sprawling hooked-spine Baja endemics and former Mammillaria species reborn as a genus after the Breslin 2021 revision. Outsized flowers from tiny bodies drive strong collector demand.

Mammilloydia

Snowball Cactus

Monotypic genus segregated from Mammillaria on smooth-seed characters. The snowball cactus M. candida is among the most widely cultivated Mammillaria-allied plants on the planet.

Stenocactus

Brain Cacti

Mexican wavy-rib globes with up to 100 corrugated ribs on a fist-sized body. The genus was long sold as Echinofossulocactus and remains one of the most distinctive groups in cultivation.

Thelocactus

Nipple Barrel Cacti

Bold tubercled barrels of the Chihuahuan Desert and central Mexico, with bicoloured spines and large vivid flowers. Includes the glory-of-Texas and the genus’s newest 2018-described Oaxacan species.

Acanthocereus

Barbed-Wire & Fairy Castle

Night-blooming, sharply angled columnar and sprawling cacti of the warm Americas. Home of the barbed-wire cactus and its mass-market fairy castle monstrose cultivar.

Aporocactus

Rat Tail Cacti

Mexican epiphytic and lithophytic trailing cacti with slender pendant stems and vivid day-blooming magenta flowers. Home of the rat tail cactus, a 300-year houseplant and the site’s first forest epiphyte.

Myrtillocactus

Blue Myrtle & Garambullo

Blue-glaucous columnar tree cacti of Mexico and Guatemala, source of the edible garambullo fruit and the standard grafting rootstock for rarer species. Home of the viral crested boobie cactus.

Cleistocactus

Monkey Tail & Silver Torch

Slender Andean columnar and pendant cacti whose narrow tubular flowers barely open, built for hummingbirds. Includes the soft, hair-cloaked monkey tail, a Bolivian cliff endemic.

Common questions about cactus types

What are the main types of cactus?

The main types of cactus are grouped by growth form: flat geophytes such as living rock (Ariocarpus) and peyote (Lophophora), eight-ribbed star cacti (Astrophytum), globular barrels (Ferocactus) and pincushions (Mammillaria), banded hedgehogs (Echinocereus), and tall columnar torches such as San Pedro (Echinopsis). Each genus links to a full profile below.

How can I tell what kind of cactus I have?

Start with the body shape and ribs, then the spine pattern, then where the flower opens. A flat tuberculate body that mimics rock points to Ariocarpus or Astrophytum; tight pectinate spines on a small button suggest Epithelantha or Mammillaria; a tall ribbed column with short spines is a Trichocereus or Echinopsis. Compare against the genus profiles below to confirm.

What is a living rock cactus?

A living rock cactus is Ariocarpus, a genus of flat, slow-growing, spineless cacti from the Chihuahuan Desert whose tuberculate bodies mimic cracked limestone and sit nearly flush with the ground. They are among the most sought-after collector cacti and are protected under CITES Appendix I.

What is the difference between a cactus and a succulent?

All cacti are succulents, but not all succulents are cacti. A cactus belongs to the family Cactaceae and bears areoles, the felted cushions that produce spines and flowers. Stone-mimics like Lithops (family Aizoaceae) and Pseudolithos (Apocynaceae) are succulents we also grow, but they are not cacti.

Which types of cactus look like stars or rocks?

Star-shaped cacti are Astrophytum, above all the eight-ribbed star cactus (A. asterias), while the rock-mimics are Ariocarpus, the living rock cacti. Both are flat, mostly spineless and ground-hugging, which is why beginners confuse them; the continuous ribs of Astrophytum versus the separate triangular tubercles of Ariocarpus tell them apart.