Cactus Species Search

State:

Arizona California Colorado Idaho Kansas Montana Nebraska Nevada New Mexico North Dakota Oklahoma Oregon South Dakota Utah Texas Washington Wyoming

Genus:

Ariocarpus Bergerocactus Carnegia Cereus Coryphantha Cylindropuntia Echinocactus Echinocereus Echinomastus Epithelantha Escobaria Ferocactus Glandulicactus Grusonia Mammillaria Opuntia Pachycereus Pediocactus Peniocereus Sclerocactus Stenocereus Thelocactus

Flower Color:

Green Orange Pink, purple Red White Yellow

Form:

Barrel Branched, cylindrical Branched, flattened pads Disc Tall, columnar Small cylinders Small globes

Name:

Cacti are the most distinctive plants of Southwest USA, and the majority occur in the four southernmost states of California, Arizona, New Mexico and Texas, especially in the Sonoran, Mojave and Chihuahuan deserts, where they are very widespread and numerous. Further north, some types like opuntia and echinocereus are still quite abundant, while there are also a number of smaller plants with much more limited distribution, such as the sclerocactus and pediocactus species.

The six cactus genera with the largest number of species, and hence most likely to be encountered, are cereus, cylindropuntia, echinocereus, ferocactus, mammillaria and opuntia.

Less common genera include ariocarpus, coryphantha, echinocactus, echinomastus, epithelantha, escobaria, glandulicactus, grusonia, pediocactus, sclerocactus and thelocactus, while the rarest genera (with the number of US species), are acanthocereus (1), ancistrocactus (2), astrophytum (1), hamatocactus (1), lophophora (1) and neolloydia (1), plus a few that occur only in Florida.

State cactus species lists: Arizona, California, Colorado, Nevada, New Mexico, Texas, Utah.

Key to the major cactus genera


Common Southwest Cactus Genera

Cereus
Cereus and related species are tall, often tree-like cacti, and only three are common in the Southwest: the saguaro (carnegia genus), senita (pachycereus genus) and organ pipe (stenocereus genus). The latter two occur most visibly in Organ Pipe Cactus National Monument but the saguaro is widespread, one of the universally recognized symbols of this region.

The only other cereus-like plants in the US include bergerocactus emoryi in southern California and peniocereus greggii in south Arizona, New Mexico and Texas. Many more varieties of columnar cacti are found in Mexico, Baja California and South America.


Cylindropuntia
Cylindropuntia (cholla) cacti are a variety of opuntia that have slender, cylindrical stem segments instead of flat, rounded pads, but share other traits including branching profusely to form large clumps, and having small bristles (glochids) in addition to the regular spines.

The majority of species have a very dense covering of spines, sometimes completely obscuring the green stems beneath, and cholla are a familiar sight across a variety of Southwest habitats, from the hottest deserts of Arizona and California to the grassy plains of New Mexico. Most species flower abundantly. Spines are covered by a thin, papery sheath, a feature not present in the opuntia.


Echinocereus
Known generally as hedgehog cactus, echinocereus is a common, widespread genus characterized by low clumps of cylindrical or conical stems, sometimes containing a hundred or more segments, and conspicuous red or pink flowers. They grow over a wide range of environments, from the low, hot deserts to cool mountain slopes, but most prefer unshaded conditions.

Spines are arranged along vertical ribs, and are always straight, never hooked. There is quite a wide variation in appearance even within individual species, with various subspecies recognized, and it can be difficult to identify a particular specimen.


Ferocactus
Ferocactus (barrel cactus) plants are characterized by many heavy spines, growing along prominent ribs, and they include the large, common and widespread barrel cacti found in the hottest parts of the deserts of Arizona and California, some becoming up to ten feet high.

There are also two less common US species - ferocactus viridescens in far southwest California, and ferocactus hamatacanthus in Texas and New Mexico. As with cer eus, far more varieties of ferocactus are found further south in Baja California and Mexico.


Mammillaria
Mammillaria are generally small, often delicate plants, usually forming clusters, with a wide variety of color, spination and flowers. Spines grow at the end of small tubercles rather than ribs - a characteristic shared with certain other, less numerous genera such as coryphantha and escobaria - and often include one of more longer central spines, which may be straight (pincushion cacti) or curved (fishhook cacti), surrounded by smaller radial spines.

Flowers come not from the apex but lower down, in a ring around the upper part of the stem, and this helps to distinguish them from similar species, as these tend to flower from the tip.


Opuntia
Opuntia ('prickly pears') are branched, joined cacti, usually densely spined, though a few species have no spines. They are characterized by flattened pads, unlike the related cylindropuntia genus (cholla), where the pads are cylindrical. Some opuntia become large and tree-like while others stay at ground level, often forming extensive mats.

There are many Southwest varieties, often similar in appearance, a few hybridized and many difficult to identify. The regular spines are surrounded by tiny bristles known as glochids, which are very irritating to the skin if touched.



Other Southwest Cacti Genera