Monday, May 24, 2010



What do a cactus and a porcupine have in common? They both have spines sticking out. They have spines for the same reason—to protect themselves from enemies. Sharp spines make them hard to eat.

The cactus uses its spines for other things, too. The spines cast shadows on the plant to shade it from the Sun. Water collects on the spines and drips down to be taken up by the roots.


There are many kinds of cactus plants, but most grow in deserts and other dry places. These plants have adaptations, or special features, that let them live in places where there is little water.

Imagine only having to take one big drink of water two or three times a year. That’s all the water a cactus plant needs. The cactus is made up mostly of stems and roots. Most kinds of cactus have no leaves or leaves that are very small. The cactus is made for storing water, and water can escape through leaves.

The roots of a cactus spread out close to the surface of the ground. When it rains, the roots soak up as much water as possible. Cactus plants do not grow close to one another. Each plant needs lots of room to collect water. The stem of the cactus stores the water for later use.


The biggest kind of cactus is the saguaro. If you drive through the state of Arizona, you will see these huge cactuses standing like trees on the dry hills. A fully grown saguaro can be 50 feet (15 meters) tall! That’s as tall as a five-story building.

A saguaro grows very slowly. At first the trunk of the plant looks like a prickly green pole. After it gets about 15 feet (about 5 meters) tall, it grows branches that curve upward. Saguaro can live as long as 150 years. An older plant can have 20 or more branches. Owls and other small desert animals make homes in the stems of the saguaro.


When spring rains fall on the desert, the cactus plants bloom. Beautiful yellow, red, orange, and white flowers appear on cactus plants. These flowers grow singly rather than in bunches. The flowers of the saguaro are creamy white and grow on top of the stems. The saguaro blossom is the state flower of Arizona. The Christmas cactus often has beautiful pink or red flowers around Christmastime.

The cactus also produces fruit that is an important source of food for desert animals. People sometimes eat the saguaro fruit.


Cactus plants are easy to take care of. You don’t have to water them very often! People like to grow them at home. This popularity isn’t so good for the cactus. People collect the plants from the desert to sell. Several kinds of cactus are now endangered in the Southwestern United States and northern Mexico.

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Christmas Cactus

The Christmas cactus often blooms around Christmastime.

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Barrel Cactus

Some cactus plants are shaped like barrels. The largest barrel cactus can grow as tall as 10 feet (3.3 meters).

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Prickly Pear Cactus

The prickly pear cactus is found throughout the Southwestern United States, Baja California, and the Sonoran Desert region of Mexico. Prickly pear cacti grow fruit that people can eat.

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Organ Pipe Cactus

The organ pipe cactus looks like a pipe organ. It grows in parts of Arizona and northern Mexico.

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Saguaro Cactus

The saguaro is the largest type of cactus. Saguaros can grow as tall as 50 feet (15 meters)! They grow very slowly, approximately 1 inch (2.5 centimeters) per year.

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