Who’s standing tall and alone?

A striking sight in the Sonoran desert is a lone saguaro cactus.

Saguaros (Carnegiea gigantea) provide food and shelter to a surprising number of creatures. This includes humans, who harvest their fruit, and use their skeletons for fences and construction.

These cacti have an amazing variety of adaptations to the desert.

First, check out the color of the stems, a pale green, indicating they contain chlorophyll. Since saguaros do not really have leaves, the stems have to do the work of photosynthesizing and producing food. The pale color keeps the plants from absorbing too much hot sunlight and getting burned.

If you look closely, you will see lines of defensive thorns on vertical accordion ridges. The whole plant can expand to hold more water after a good rain, then accordion back in as it uses the water

What you can’t see is the root structure. Instead of sending down a big tap root, like many plants, they send out numerous very long horizontal roots near the surface, to better gather any moisture nearby.

That’s why they’re lonesome looking—they need to grow far apart. And that’s why, in the old days before we realized it was unethical, (now it’s also illegal) people would dig them up in the desert, transplant them, and they would die, because the majority of  the root structure was left behind.

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Leafing so soon?

There are leaves and then there are leaves. And then there are cactus pads, like this wide flat prickly pear cactus pad, which are more like stems than leaves.

Because if you look closely, on the surface of this pad, you will see the actual leaves, small succulent pointy cones, next to their associated thorns, which form in the axil (that’s like the armpit!) of the leaves.

The thorns persist, as most desert dwellers know too well, but the little leaves fall off in a matter of days, another water-saving feature, so only the thorns and the thick-skinned pads, and the quickly hardening new pads, remain.

Stems or not, the pads, after the skin and thorns are very carefully removed, have been used for centuries as food by native civilizations in the desert

 

Packrat Middens

Packrats, Neotoma albigula, make interesting nests in which to store their treasures—and themselves.

When you are out in the desert, the trick is how to spot a packrat nest. It’s not always easy. I guess that’s the idea, when you are building a hideaway.  Basically, look for a crazy, almost random pile of sticks and leaves, and often cholla cactus stems. The nests can range from a foot to 8 feet wide, and are often at the base of a shrub or cactus.

Apparently, If you went inside a packrat nest or midden, an activity the packrats vigorously discourage, you might find shiny bits of human treasures—foil, metal, or other bright objects, since packrats seem to like shiny things as much as we do.

Packrats do like cholla cacti, somehow managing to avoid their really nasty and determined thorns. There’s even one variety called the jumping cholla—I would stay away from those! The name comes from how easily a stem can get detached and glom onto you. A packrat favorite! Cholla stems are certainly a good defensive addition to a habitation—the dry stems are probably even nastier than green ones. According to the Desert Museum, packrats love to eat prickly pear fruit. So they are really cactus creatures.

Choose native plants for your desert landscape

One way to figure out what plants will be suitable and attractive in your desert landscaping is to go to a nearby natural area and see what is growing wild.

Make sure you select a location that is similar to yours in exposure, dryness and altitude.

Take photos or make a list of plants you find attractive. Never dig up native plants! They are fragile and rare, and in most places it is illegal to do so.  Almost everything you will see is available in plant stores. Photos will also help you arrange your landscaping, showing which plants grow together, and how much space they need.

Then go to the web or in plant books to learn about the plants you have found, or take your photos to a local nursery that specializes in native plants, and decide which are for you.

The variety of desert plants is surprising: cacti, shrubs, vines, spring-flowering annuals, many kinds of perennials. A big virtue of native plants is that they  require little in the way of extra water and plant food, and are easy to maintain.

One thing to keep in mind about native plants–some of them grow very slowly, so it may take a while for your landscape to mature. But there is nothing to match their beauty, and their ability to attract native fauna.

Why does the cactus look like that?

The first thing you notice about a cactus is generally the spines. Some have short, nasty little almost invisible fishhooks, some inches-long needles. Then there’s the form of the plant. Most cacti are plump, rounded, often stubby. They tend to be grayish-green in color. And they usually do not have obvious leaves.

Why?

Whenever you come across questions like this, think about the ecosystem where the organism lives. Cacti live in dry climates with a lot of sun, and few other plants, especially leafy ones.

So keeping cool is an issue. A light neutral color does not absorb a huge amount of the sun’s heat. There are very few plants with dark bark, or skins, or leaves in the desert.

Retaining moisture is perhaps the most important issue for a desert plant. The blunt, compact shape of cacti, their thick skins, and lack of leaves are all moisture-conserving features.

And lastly, toothsome, moist leaves would attract all kinds of herbivores. So the lack of leaves discourages plant-eaters, and the big spines and tough hide protect any soft, moist tissue a cactus does have.

Spring begins in the Sonoran Desert

Tour images of the desert in spring.
Early spring in Sonoran Desert mountains.