Many people are familiar with a stylized image of a tall, many-armed cactus. This image has become nearly synonymous with the American west, deserts, and cowboys. However, not as many people know that this particular cactus is called the saguaro, and even fewer people know about its fascinating place in the ecosystem of the Sonoran Desert.
What Does a Saguaro Look Like?
- 10 to 60 feet tall
- Up to 50 arms
- Dark green and ribbed
- White flowers in the spring
Saguaro cacti are large plants, growing to between 10 and 60 feet tall when fully mature. They're usually about 30 inches in diameter, and they can grow about 50 arms, although they usually sport far fewer. Some saguaros may have no arms at all.
Succulents with Protection
Saguaros are sage green in color, and their trunks and arms are deeply ribbed and covered in long needles, which can be up to 3 inches in length. These needles, sometimes also referred to as spines, help to protect the cactus from predators. The cacti are succulents, which means they can store great amounts of water, and the spines help to protect those reserves.
As saguaros store more water, their skin expands to accommodate the extra weight. Saguaros can become heavier and heavier, and you may even notice that they seem quite bloated. This water will be consumed later, during drought periods.
In spring, usually from April to June, you can spot saguaros in bloom. The cacti produce large white flowers with yellow stamens. The flowers appear only at the very top of the cactus and at the tips of the arms. After pollination, the flowers give way to red, oval-shaped fruit, each of which contains thousands of tiny seeds.
Habitat and Range
Although they have come to represent a wide range of deserts, saguaros are actually only found in the Sonoran Desert. In the United States, you can spot the cacti in southern Arizona and occasionally in southeastern California. In Mexico, they're found in western Sonora.
Saguaros are, like many cacti, well-suited to extremely warm, dry weather, although they can suffer in extreme droughts. These cacti can only tolerate freezing temperatures for a matter of hours.
The Life Cycle of a Saguaro Cactus
- 1% of seeds germinate
- Young cacti can take dozens of years to grow
- Lifespan of 150 to 200 years
The saguaro cactus takes a very long time to grow. These cacti generally live for between 150 and 200 years, and it can take a saguaro thirty or more years to grow just 3 feet. When they're young, saguaros may only grow a few inches at a time, and a cactus that's 10 years old may only just poke above the ground.
Saguaros produce a large number of seeds because only about 1% of all seeds will successfully germinate. Seeds must have enough water to germinate, so a drought year can mean an even lower germination rate. Successful sprouts will take root under nurse plants such as palo verde trees and desert willow. These plants help to shade the young cactus, protecting it from drought and offering cooler temperatures.
As the saguaro matures, it will develop a strong root system. A central taproot will reach into the earth, extending down as far as 3 feet. Most of the saguaro's other roots will only be about 4 or 5 inches deep, but this root network can extend for up to 100 feet in all directions around the cactus.
How Often Do Saguaros Sprout Arms?
Many myths surround how often a saguaro grows an arm. You might hear some that say the cactus will grow a new arm every 10 years, while others say every 25 or 50 years. In truth, some saguaros simply sprout more arms more frequently, while others may never grow an arm at all.
About one in 10,000 saguaros will grow differently thanks to either a genetic, fungal, or bacterial anomaly. These cacti are known as cristate saguaros and form rounded, spiraled tops instead of tall spears and branches.
A Keystone Cactus
- Food for bats and birds
- Excellent nesting sites
- Saguaro skeletons used traditionally as building material
The saguaro cactus plays a crucial role in the ecology of the Sonoran Desert. The nectar the cacti's fruit produces draws in bats, doves, finches, hummingbirds, honeybees, orioles, and woodpeckers. These creatures all also aid in pollinating the saguaro flowers. Bats and doves also enjoy feasting on the fruit of the saguaro and, in return, help to spread saguaro seeds.
Saguaros are also a popular nesting site for different bird species. Many woodpeckers drill directly into the saguaros, creating holes. The spines surrounding the nesting holes help to protect both the eggs and baby birds. These nest holes are often used by other bird species the following year. Owls and wrens are often seen nesting in old woodpecker holes.
People have also traditionally used the saguaro cactus as a source of sustenance and material. You can eat both the fruit and seeds. Fruits can be made into jams and syrups, and the seeds can also be fed to chickens. When a saguaro dies, the sturdy ribs can be used to make tools, fencing, furniture, or even as a roofing material. Areas where birds have excavated a deep nest often callus over, creating what's known as a saguaro boot. These boots were traditionally used as baskets.