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    Saguaro

    National Park Arizona

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How Saguaros Grow

Saguaros are a very slow growing cactus. In Saguaro National Park, studies indicate that a saguaro grows between 1 and 1.5 inches in the first eight years of its life.

 
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Reddish-green saguaro seedling beginning to emerge from tiny black seed
NPS PHOTO
 
These tiny, young saguaros are very hard to find as they grow under the protection of a "nurse tree", most often a palo verde, ironwood or mesquite tree. As the saguaro continues to grow, its much older nurse tree may die. Some scientists believe that competition from the saguaro may lead to the death of the nurse tree by taking water and nutrients from the soil in the immediate area.
 
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Young saguaros growing under the protection of mesquite "nurse tree"
NPS PHOTO
 
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Saguaros with first branches

NPS PHOTO

As a saguaro begins to age, growth rates vary depending on climate, precipitation and location. We do know that the period of greatest growth in a saguaro cactus is from unbranched to branched adult.

Here at Saguaro National Park, branches normally begin to appear when a saguaro reaches 50 to 70 years of age. In areas of lower precipitation, it may take up to 100 years before arms appear.

 
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Saguaro flowers in bloom

NPS PHOTO

When a saguaro reaches 35 years of age it begins to produce flowers. Though normally found at the terminal end of the main trunk and arms, flowers may also occur down the sides of the plant. Flowers will continue to be produced throughout a saguaro's lifetime.
 
An adult saguaro is generally considered to be about 125 years of age. It may weigh 6 tons or more and be as tall as 50 feet. The average life span of a saguaro is probably 150 - 175 years of age. However, biologists believe that some plants may live over 200 years.
 
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Mature saguaros
NPS PHOTO

Did You Know?

Javelina

"Don't call ME pig!" Javelinas are able to eat spiny prickly pear pads with no obvious harm to their mouths, stomachs or intestinal tracts due to an enzyme in their saliva. Javelinas are not true pigs, they are peccaries, which are native to the Americas. True pigs are native to Europe and Asia. Wild pigs and boars are descended from true pigs brought over on boats to the new world.