CHIHUAHUAN DESERT CACTI

The Chihuahuan Desert does not have the large, spectacular, columnar cacti associated with the Sonoran Desert, such as the saguaro, cardon, organ pipe and senita. But it has many small cacti and interesting cacti that are found nowhere else in the world.

Perhaps the best known example is the peyote (Lophophora williamsii) which has a long tuberous root and only a small part of the plant is seen above ground - as a greyish button. This cactus was once common but is now rare because the plants have been harvested and sold for their hallucinogenic properties. It has been almost eliminated from the small region of Texas where it once occurred - the extremely dry limestone ledges and hills (see image below) of the Big Bend National Park. But small populations still remain in northern Mexico.

Limestone ridge, Big Bend National Monument, Texas

Living rock cactus

The living rock cactus (Ariocarpus fissuratus) is an equally strange plant, with a large, turnip-like taproot. Its above-ground part consists of a rosette of triangular tubercles which have no spines and which blend in with the stones and rocks on the limestone ledges. The compound image below shows some examples, all photographed in the type of environment shown above.

Click on different parts of this image to see larger versions

Ariocarpus fissuratus is the only species of this genus that occurs in the USA, although five other species of Ariocarpus are found in the Chihuahuan Desert of mainland Mexico. All are protected plants in the regions where they occur. Many exist as only small, isolated populations and are in danger of extinction because they sought by plant collectors.

The thick taproot serves for water storage. The above-ground part consists of triangular, warty, spineless tubercles that are camouflaged remarkably well against the limestone chippings among which they grow. In times of severe drought the whole above-ground portion can shrink and be covered, but the taproot remains alive. These plants often have a woolly centre, from which bright pink-violet flowers emerge in autumn.

Boke's button cactus

The Boke's button (Epithelantha bokei) is also known as the smooth button. In times when water is available it is an almost completely rounded cactus, with small tubercles that are completely obscured by the very dense coating of tiny white spines. In times of extreme drought it shrinks into a concertina-like form (see images below). These specimens were photographed close to the living rock cacti on a limestone outcrop.

Eagle claws (or Turk's head) cactus

The eagle claws cactus (Echinocactus horizonthalonius) is is a small barrel cactus, usually rounded in form and reaching a diameter of about 15 cm. It is quite common on limestone or lime-rich soils of parts of West Texas, New Mexico and in the Chihuahuan Desert of Mexico. There is also an isolated population in a limestone area of Arizona, where it can grow in a columnar form, up to 30 cm tall.

As shown in the left-side image above, this cactus is characteristically grey-green in colour, with a small number of broad ribs and deep grooves between them. The ribs are covered with stout red spines that curve like an eagle's claw. The image on the right side above shows a variant or a related species.

Cat claw cactus

The cat claw cactus (Ancistrocactus uncinatus) is a small barrel-shaped plant, about 15 cm tall, with ribs composed of fused tubercles. It is found on limestone soils in the Chihuahuan Desert of southeastern New Mexico, sothwest Texas and Mexico. The body of the plant has a bluish colour but the most conspicuous feature is the combination of long red-coloured spines, often hooked at their tips, and long straw-coloured spines. All these main spines project far above the top of the plant. In this image the cactus is seen growing next to lechuguilla (a characteristic Chihuahuan Desert species of Agave with sharp, banana-shaped leaves) rooted into a crack in a limestone rock.

Rainbow cactus

The Texas rainbow (Echinocereus pectinatus) is one of several rainbow cacti that have ribbed stems (not tubercles) with very closely spaced areoles. The spines from these areoles often almost completely cover the stem, providing protection from intense sun. As the plants grow from the top of the stem the spines that they produce in different years or different times of the year can have different colours. This results in a banded pattern of spine colours - hence the name "rainbow" cactus.

There are several types of rainbow cactus in different desert regions, but the Texas rainbow is common in the Chihuahuan Desert of Mexico and in restricted regions of southern New Mexico and Texas.

Hedgehog cacti (Echinocereus species)

There are many species and varieties of hedgehog cacti, all belonging to the genus Echinocereus. They typically produce clusters of erect stems, up to 30 cm high. The ribs that run up the stems have areoles that produce long, sharp spines, which stick out like the spines of a hedgehog. Most of these cacti produce bright, showy flowers from short flowering branches that emerge behind the growing tip of the stem.

The individual species are difficult to tell apart because they hybridise. The most widespread species is the claret cup (Echinocereus triglochidiatus), which is variable but always recognisable by its bright red flowers with rounded petal margins. This species occurs mainly in upland and mountain zones rather than in the deserts. In contrast , Engelmann's hedgehog (Echinocereus engelmannii) is a true desert dweller, being found mainly in south-central Arizona and westwards into southern California. Several other types of hedgehog cactus are found in the Chihuahuan Desert.

Several other hedgehog-type cacti occur in the Chihuahuan Desert, such as the two examples below, both of which are growing in arid conditions on limestone substrates. In the left-side image the cactus is growing alongside lechuguilla - a drought-tolerant species of Agave, characteristic of the Chihuahuan Desert. In the right-hand image the neighbouring plant is different, even though it might look like lechuguilla. Its leaves have a red colour and rows of spines along the leaf margins. This plant is the drought-tolerant Hechtia texensis - a member of the pineapple family.

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