Boomer Bear takes a look at how cactus and critters share their Sonoran Desert home.

If you’re drawing a picture of our desert, chances are you’re going to include at least a few prickly plants, since cacti—especially saguaros—are such an ICONIC part of our beautiful desert.

Lucky to Live in a Lush Landscape

Arizona actually has part of all four major deserts of North America. But our Sonoran Desert is one of the most beautiful in the world! When people think of deserts, they usually think of an unbearably hot, dry and barren place. Although times of drought do hit here, two rainy seasons can bring a foot or more of rain during a good year!

“We have two rainy seasons, one in winter and one in summer. We get a little over half of our rainfall in summer and a little less in winter,” points out Robin Kropp, education specialist for the Arizona-Sonora Desert Museum. “It is quite lush here compared to many deserts. Some scientists think that the Sonoran Desert landscape around (here) shouldn’t even be CLASSIFIED as a desert because it is so rich in plant life.” In winter and early spring, other deserts have colder temperatures than here.

But our native plants, including cactus, need to be tough enough to survive long periods of drought and occasional freezing temperatures. “One of the things that makes a desert a desert is that rainfall patterns can be extreme. Sometimes we get very little throughout the year (drought). Sometimes we get a big downpour in one storm, and that ends up being a big portion of the year’s rain!” Kropp explains.

“Cacti are special because they are adapted to survive long periods without rain by storing water inside like a built-in water bottle. They can live off this stored water until it rains again,” she says.

What Is a Cactus?

Cacti come in all different shapes and sizes from towering tall ones to ones that barely poke up from the ground. They are special succulents of the family Cactaceae. Like other succulents, cacti have soft tissue that can store lots of water, which the plant uses during dry conditions.

“Cactus plants have these main features that distinguish them: thick, waxy skin that holds the stored water inside; water-storing tissues; and flowers with many petals, pollen-bearing parts, and lobed female parts,” Kropp explains. Instead of having leaves, “many cacti are covered with spines as well. You probably know that they keep many animals away from the cactus’ body. They help protect their stored water from thirsty animals. But another important reason that they have spines is protection from the sun—spines make little bits of shade all over the plant, kind of like the cactus’ sunscreen.”

Origins of Cacti

Surprisingly, scientists found that the first cacti didn’t grow in desert areas! And, they haven’t been around as long as more primitive plants like ferns and cycads, which first sprouted some 300 million years ago.

The first flowering plant bloomed more than 174 million years ago. But cacti are sort of the new kid on the block, according to botanists who study them.

“Cacti appear about 35 million years ago. They are definitely newer, very recent arrivals,” explains Raul Puente, curator of collections for the Desert Botanical Garden in Phoenix. “The center of origin is considered to be the Andes region of South America—right in the corner between northern Argentina, northern Chile and Bolivia.”

From there, these spiny plants spread in all directions. The ones that headed northwest went well beyond what is now Mexico and Arizona. Cactus seem to adapt well to everything but extreme cold. “You can find them in the tropics, even in rainforests,” Puente notes, “all the way up to the lower third of Canada. So they have been extremely successful, able to colonize a key portion of the continent. They thrive not only in the desert—that’s the last area that they occupied!”

Lots of Desert Critters Depend on Cacti

No, you don’t want to hug a cactus, but several desert dwellers RELY on them.

“Some birds, like Gila woodpeckers and some other species of woodpeckers like flickers, carve their nests into the stems of saguaros and other species of columnar cactus. And then the same cavities later on can be occupied by other animals like elf owls around here,” Puente says.

Larger raptors (hunting birds) like hawks, caracaras and even bald eagles will make big nests in the arms of a saguaro!

A variety of critters feed on cacti. “Birds that eat fruit, a lot of rodents, too. You’ll see rodents survive by eating the fruit or feeding on other parts like cactus stems, flowers or roots,” Puente explains. “Then you have bigger animals like javelina or coyotes—many species eat the fruits of prickly pear and barrel cactus or even cholla.”

Saguaros Are Incredible

Growing up to 75 feet, saguaros (Carnegiea gigantea) are the tallest native plant in the Sonoran Desert. And for many folks, the saguaro is the symbol of our desert and the West!

They are a columnar cactus, meaning they have vertical ribs, which function like an accordion, expanding when the plants take in water and folding as that water is used. And after our recent rains, there are plenty of chubby saguaros out there, weighing up to 4,800 pounds! This wet winter weather will make for spectacular white blooms on these saguaros.

These large flowers attract bees, other insects and at night, bats! In fact, saguaros and other cacti have adapted to being active in the desert night, when temperatures are cooler and when they won’t lose as much water as when it’s hot and sunny.

The bulk of the flowers are open at night. Then at night they are pollinated by bats! Some species go after the nectar, which is the reward for the pollinators, including the bees. Once pollinated, each flower turns into a delicious, juicy red fruit filled with 400–800 seeds. Birds and other desert critters ingest those seeds and carry them off, eventually pooping them out. If the bird is perched on a shrub or tree branch, a fortunate saguaro seedling will start its early years growing under the protection of a nurse plant, which can provide shade and moisture. Saguaros, which can live 175 years or more, are just some of the protected plants here in Arizona. And all plants in a National Park are protected and cannot be removed.

If you want to see and learn about cactus and other desert plants, plan a family or class outing to the Desert Botanical Garden in Phoenix (visit dbg.org for details) or the Arizona-Sonora Desert Museum west of Tucson (desertmuseum.org).