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5 Saguaro Cactus Science Fun Facts We Learned on Our Trip

 

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Recently, we traveled to Arizona and Visited Saguaro National Park. Everywhere in the park, there were saguaros (pronounced “suh-wahr-oh”) as far as the eye could see. Did you know that saguaros are among the oldest living things on Earth? These giant cacti have been around for millions of years.   We discovered some fun science facts about the saguaro cactus and wanted to share them with you.

Saguaro Cactus Only Live in One Desert on Earth

 

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The only desert the saguaro cactus live in is the Sonoran Desert. This desert is primarily in Mexico but covers most of the southern half of Arizona and a small part of southern California. However, they don’t grow everywhere in the Sonoran Desert. Because saguaro cacti thrive in hot weather, they only grow from sea level to about 4000 feet in elevation. Cold weather at higher elevations can kill the cactus.

 

The Life Cycle of the Saguaro Cactus

 


This palo verde acts as a nurse plant for the saguaro cactus near its base.

Baby Saguaro

Saguaro cactus starts from a black seed that comes from the plant’s fruit. A saguaro grows slowly for about the first five years of life, growing about an inch to an inch and a half a year. Most of those that survive grew under a “nurse tree.”  Nurse trees include palo verde, mesquite trees, or ironwood trees. Being under another tree makes it hard for predators to find a baby saguaro.

saguaro-flowers

Young Saguaro

Young saguaro cactus grow faster. When they are about 35 years old, they start producing flowers. Flowers grow at the top end and sometimes on the sides of the plant. When the cactus is about 50 years old, it may start growing arms. Flowers also develop from the tips of the arms. These flowers produce reddish fruit. Each fruit can hold up to 2000 seeds.

Adult Saguaro

A saguaro cactus is considered an adult when it reaches 125 years old—the average saguaro lives to be between 150 and 175 years. An adult can be 40 to 60 feet tall and weigh up to 4,800 pounds. When the cactus has stored a lot of rain, it weighs the most.

 

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Saguaro Cactus Fruit in Southwestern Sonoran Desert with Cactus Wren

 

Pollinators of the Saguaro Cactus

Saguaro Cactus that produce flowers do so from April to June.  Each flower blossoms for about 24 hours.  An individual flower opens at night and closes the next afternoon.  In order for fruit to form, the flowers need to be pollinated during this time.  At night, bats pollinate the flowers.  During the day bees, butterflies, and birds: especially white-winged doves pollinate the blooms.

 

Saguaro Cactus Make Many Adaptations

 

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Ok, so we did know that cacti make many adaptations since we wrote the book Plant Adaptations: How We Live in Our Habitat. But, we want to share these fantastic adaptations with you!

What is an Adaptation?

An adaptation is a body part or behavior that helps a plant or animal survive in its environment. One of the most striking features of saguaros is their ability to adapt to their environment.

 

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Thick, Waxy Skin

The outer coating of the saguaro cactus is thick and waxy. This helps the cactus to survive extreme temperatures and dry air. The wax helps prevent moisture loss by slowing it down.

Root System

This cactus has one deep taproot. The taproot goes down more than two feet and gets water deep in the ground. The saguaro also has a root system close to the Earth’s surface. They are about four inches underneath the dirt and rocks. As the cactus grows, the roots spread even further. They radiate out as far as the cactus is tall. These roots quickly collect rainwater when it falls. Just like other plants, the roots of this plant also collect nutrients from the ground and help hold the plant in place.

Spines of the Saguaro Cactus

 

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observe the downward position of the spines

 

The spines of the saguaro are modified leaves. The spines serve many functions. Most spines point downward to help rainwater go into the ribs on the stem. The spines give the cactus shade during the day and help keep the cactus warm at night. They help prevent water loss from dry winds. These modified leaves also protect the cactus from thirsty and hungry predators.

 

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Note the ribs inside this dead saguaro cactus.

Thick, Ribbed Stem

The stem of the saguaro cactus protects the woody ribs inside it. The ribs can expand like an accordion when it rains. This way, the plant can hold more water.

 

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A pair of birds nesting in a saguaro cactus

Saguaro Cactus Provide Homes to Many Birds

Saguaros often have many holes in them.  Gila Woodpeckers and Guilded Flickers make holes in saguaros to nest in.  The nests are made between the outer layer and the interior woody ribs.  It provides a safe place to live and raise their young. After they raise their young, they leave.  Then other birds such as cactus wren, elf owls, screech owls, purple martins, finches, and sparrows make their homes in the cavities.

 

Just Two Rainy Seasons

The saguaro cactus survives with just two rainy seasons a year.  December and January are one rainy season and July through September is another one.  An average of 13 inches of rain falls in Saguaro National Park during this time each year.  When it rains a saguaro can absorb up to 200 gallons of water.  That’s about four bathtubs full of water.

Do you want to see more of the desert in bloom?  Read about our trip to the Desert Botanical Gardens.

If you want your students to learn more about desert plant adaptations, we have some resources for you. Desert Plant Adaptations has a text about the desert and a text about cactus adaptations.  It comes with graphic organizers and links to sites for student research.

desert-plant-adaptations-resource-for-students

One of our top sellers is our Plant Adaptations resource. You can find that here.

And remember, it’s all science!

Sarah

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