Nature Profiles

Cacti and Succulents of the Sonoran Desert

For many outsiders, Arizona is typified by one group of plants - the cacti.  They are found across the state, even in woodlands and as high as 2500m in the mountains.  The real icon of the family, the saguaro, is found in many areas of central and southern Arizona in the Sonoran Desert.

Carnegia gigantea (Saguaro)

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Saguaro NP West

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Spine detail, Saguaro NP West

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buds in spring, Sabino Canyon, Santa Catalina Mountains

Surely the most most recognisable plant in the whole of the United States, for many the saguaro symbolises the Sonoran Desert. 

Because of its sensitivity to frost, the saguaro's distribution is often limited to rocky slopes away from valley floors which are colder in winter.  Almost all of the United States' saguaros are found in Arizona, with a few just over the border along the far eastern edge of California. 

Saguaros are long-lived (often to over 100 years and it can take over 50 years for a seedling to mature into a flowering adult plant), and as they age they play a vital role in the desert ecosystem.  Their fruits are an important food source in late summer for many animals, and the trunks are used by birds such as Gila Woodpeckers and Elf Owls as nesting sites.

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Unusual down-curved arms, Saguaro NP West

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Cristate Saguaro, Saguaro NP East

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Saguaros in bloom and bud, Sabino Canyon

 

 

Echinocereus engelmannii (Strawberry Hedgehog Cactus)

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var. acicularis, Silver Bell Mountains, Pima County

A highly variable species which is widespread throughout the Sonoran and Mojave deserts, this beautiful cactus is easily seen in Saguaro National Park. 

In spring it produces beautiful magenta flowers, and in late summer the plants are topped with bright red fruits resembling strawberries, hence the common name.

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Red Rock

 

 

Echinocereus nicholii (Nicholl Hedgehog)

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Silver Bell Mountains, Pima County

This rare plant is only found in a small area of southern Arizona, and in Sonora, Mexico.  It has a very distinctive appearance - the pink flowers appear rather small compared to the size of the tall thin stems which are densely covered in golden spines.

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Echinocereus fasciculatus (Bundle-spine Hedgehog)

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Sabino Canyon, Santa Catalina Mountains

Closely-related to the widespread and very variable E.engelmannii (see below), this cactus is sometimes regarded as merely a variety of that species.  The main distinguishing feature is in the spination - the central spines of E.fasciculatus are straight, as opposed to bent or twisted, and have brown or black tips. 

E.fasciculatus is widespread in the Sonoran Desert, ranging into adjacent New Mexico and Sonora.  Unlike E.engelmannii, it is completely absent from the Mojave Desert.

 

 

Mammillaria macdougalii (MacDougal's Pincushion)

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Box Canyon, Santa Rita Mountains

This squat cactus is often only noticed when flowering - for the rest of the year it lurks hidden amongst grasses in its canyon habitat. 

M.macdougalii is easily recognised by its thin, spreading straight spines and yellow flowers.  In the United States it is restricted to southern Arizona and adjacent New Mexico, where it grows on rocky canyon slopes in grassland or oak woodland. 

The taxonomy of this plant varies - some authorities treat it as a subspecies of the widespread M.heyderi.

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Mammillaria grahamii (Graham's Fishhook Cactus)

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Saguaro NP West

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Kartchner Caverns SP

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Saguaro NP West

The commonest Mammillaria of the Sonoran Desert, this beautiful clustering species is widespread in the Sonoran and Chihuahuan Deserts.  In common with the barrel cacti (Ferocactus) it flowers in summer rather than spring. 

Despite the delicate appearance of this plant, it is armed with vicious fish-hook spines, which can easily ensnare a carelessly placed hand as well as unwary desert animals such as lizards and even birds! 

This species can only be confused with closely-related cacti such as M.thornberi, M.mainiae and M.tetrancistra, all of which are much rarer in southern Arizona and differ in small details such as tubercle shape and spine arrangement.

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Saguaro NP West

 

 

Opuntia engelmannii (Engelmann Prickly Pear)

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all photos Sabino Canyon, Santa Catalina Mountains

A variable and widespread plant, this is the commonest and largest prickly pear species in the Sonoran Desert.  It is superficially similar to other less common species, with which it sometimes forms hybrids, but can usually be recognised by its white, evenly-sized short spines surrounded by abundant dark glochids.

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Opuntia phaeacantha (Brown-spined Prickly Pear)

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Kartchner Caverns SP

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Box Canyon, Santa Rita Mountains

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Found across most of Arizona, and absent only from the far west and south-west of the state, O.phaeacantha is very similar to O.engelmannii, but has longer, brown spines and is generally a smaller plant, although the two species readily hybridise where their ranges overlap.

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Kartchner Caverns State Park

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Sabino Canyon, Santa Catalina Mountains

 

 

Opuntia chlorotica (Pancake Prickly Pear)

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Kartchner Caverns SP

The almost circular pads and golden spines identify this prickly pear as O.chlorotica, rather than the far more common and variable O.engelmannii.  It tends to be a higher elevation cactus, occurring on rocky slopes in canyons where desert merges into grassland or woodland. 

Thanks to John Wiens for the identification.

 

 

Cylindropuntia bigelovii (Teddy-bear Cholla)

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Saguaro NP West

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Saguaro NP East

This beautiful cactus is certianly well-known in the south-west, but is definitely not a cuddly as its name suggests!  Its limbs detach easily and the sheathed spines have barbed tips which easily embed themselves into any soft object, including a hiker's arm. 

This unpleasant characteristic of the cactus is in fact a brilliant adaptation to desert life - the detached joints which fall onto the ground take root and grow into new plants which are clones of the parent.  Most of the fruits of Teddy-bear Cholla contain no seed, although a limited amount of reproduction is by this more conventional method. 

Teddy-bear Cholla is a plant of the hottest habitats within the Sonoran Desert, and can be seen in many areas of southern Arizona, as well as southern Nevada, southeastern California and adjacent northern Mexico.

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Saguaro NP West

 

 

Cylindropuntia leptocaulis (Christmas Cholla)

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Saguaro NP East

Christmas Cholla gets its name from the red fruits which persist through the winter months.  It is the most widespread of all the Cylindropuntias, from Oklahoma and Texas southwards to the south of Mexico. 

It also has the thinnest stems of any cholla - no thicker than a pencil.  Christmas Cholla is easily recognised by its grey-green, largely spineless thin stems.  It is often a low-growing plant, and can be hard to spot if no fruit is present.

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Young spring shoots

 

 

Cylindropuntia fulgida var. fulgida (Jumping Cholla)

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Saguaro NP East

The common name of this cactus derives from the unpleasant habit of its joints to fall off and become attached to unwary passers-by - a painful encounter! 

Jumping Cholla is a large-growing species which develops an obvious woody trunk and tree-like silhouette as it matures.  Superficially it resembles Teddy-bear Cholla (C.bigelovii), but the glassy spines cover the stems less densely and the flowers are dark pink rather than very pale yellow.

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Saguaro NP West

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Cylindropuntia spinosior (Cane Cholla)

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Catalina State Park

More cold tolerant than many other cacti, this plant has a high elevation range in Arizona and can be found high up into juniper woodland.  It is a shrubby species which grows to around 3 metres tall. 

It is closely related to the similar Staghorn Cholla, but can be distinguished by its spinier stems with more tubercles and broad-based fruits which are covered in prominent tubercles. 

Cane Cholla is common across the southern half of Arizona and southwestern New Mexico, as well as adjacent areas of Mexico.

 

 

Cylindropuntia versicolor (Staghorn Cholla)

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Saguaro NP West

This species is a very common cactus of the desert around Tucson.  It is a beautiful plant in flower, when the origin of its Latin name can be appreciated - the flowers come in assorted colours, even on adjacent plants in the same population.

Like the saguaro, this cactus plays an important role in the desert ecosystem, providing a safe nesting site for many birds such as cactus wrens and white-throated sparrows.

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Cylindropuntia arbuscula (Pencil Cholla)

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Fruit detail

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Saguaro NP West

In lowland areas of the Sonoran Desert you many come across this distinctive cholla.  It resembles C.leptocaulis (see above), but the individual stems are thicker, and only sparsely covered with spines.  This species also has green rather than red fruits. 

This cactus is only found in southern Arizona and adjacent parts of Sonora, Mexico.

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buds in spring

 

 


Cylindropuntia acanthocarpa (Buckhorn Cholla)

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Saguaro NP West

Rather similar in appearance to other thin-branched chollas such as Stag-horn Cholla, Buckhorn Cholla is locally common in the Sonoran Desert (and perhaps the most common cholla of the Mojave Desert to the north-west). 

It can be difficult for a beginner (like me!) to distinguish between this and closely-related species, but key features to look out for are the shape of the stem tubercles (they are much longer than wide in C.acanthocarpa) and the spiny fruits, when present. 

Like other chollas, the species is variable, with three varieties present in Arizona.

 

 

Echinocactus horizonthalonius var. nicholii (Turk's Head Cactus)

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Waterman Mountains, Pima County

This cactus is listed as Federally Endangered, and has a very restricted distribution; it is found in two of Arizona's limestone mountain ranges, and one in northern Mexico.  Within those ranges the plant can be fairly frequent, however. 

The nominate variety is a Chihuahuan Desert species, and is much more common, although it is not found in Arizona.  The combination of pale grey-green solitary stems and strong curved spines make this cactus instantly recognisable.

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Ferocactus wislizenii (Fishhook Barrel Cactus)

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Much more common in the Sonoran Desert than the similar Compass Barrel (F.cylindraceus), Fishhook Barrel can be recognised by its sparser radial spines, which leave the green stem clearly visible.  It also has between 2 and 4 central spines (1 is fishhook-shaped), whereas Compass Barrel has 4 central spines, the longest of which is twisted and points downward.

Fishhook Barrel is the domionant barrel cactus in the eastern half of the Sonoran Desert, and Compass Barrel is dominant in the west, extending into the Mojave Desert.

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Agaves & Yuccas

Agave is a large genus, with the vast majority of species being native to Mexico.  Twelve species are native to Arizona, and live in a variety of habitats, from rocky lowland desert to high altitude pine-oak woodlands.  The two species illustrated below are widespread in south-eastern Arizona, along the eastern edge of the Sonoran Desert.

Yuccas are taller cousins of Agaves, with distinct trunks.  Ten species are native to Arizona, including one naturally-occurring hybrid.

Agave parryi var. parryi (Parry's Agave)

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Kitt Peak, Quinlan Mountains

This is a common species in many rocky canyons in the Sonoran Desert.  It can be distinguished from the other common large Agave, A.palmeri, by its highly symmetrical appearance which resembles a large artichoke due to the broad, short leaves. 

Three varieties of this variable species are found in Arizona: palmeri, huachucensis and couesii, all of which have distinct separate distributions.

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Agave palmeri (Palmer's Agave)

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Route 77

This large-growing Agave is common in many areas of Arizona, a particularly oak woodland and grassland.  It favours cooler habitats than the Sonoran Desert species, and is more common in the Chihuahuan Desert. 

Size alone is a good identifying feature for mature plants of this species - fully-grown plants can reach nearly 2 metres tall.  The leaves are narrow and often banded in various shades of grey and green.

 

 

Yucca elata (Soap Yucca)

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Sabino Canyon, Santa Catalina Mountains
 

This widespread Yucca is found in the Sonoran and Chihuahuan Deserts but absent from the driest areas.  It is especially common in grassland habitats where it can be a dominant feature of the landscape. 

Soap Yucca can be recognised by its tall trunks (on mature plants) covered with dead leaves, topped by a spherical head of fresh leaves which are narrow and have their margins shredded into thin white fibres.

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