Ajo Mountain Drive Stop 3

The largest saguaros in the park can range anywhere from 150 to 200 years old.

NPS Photo/ Craig Stocks

Quick Facts

Location:

Mile 1.9 [km 3.1] along the Ajo Mountain Drive

Stop 3
 

A Sonoran Desert Icon

You would think that the saguaro cactus, which dominates the landscape, would be one of those well-adapted, hardy desert species. It is certainly the tallest and largest cactus in the United States, growing as high as 50 feet and weighing several tons. It can live to be 200 years old. In Organ Pipe Cactus National Monument we think that these cacti flower for the first time at approximately 65 years of age and might produce their first arms at around 90. Of course there is no way to know exactly how old a saguaro is (it doesn’t create growth rings like a tree). What we know comes from averaging data from hundreds of cacti all across the Sonoran Desert. Cacti living in washes or over by Tucson, where the water is more abundant, grow faster. Cacti growing in the valley flats, where water is scarce, can live their whole lives and never have the resources to support arm growth. A saguaro is entirely dependent on location and rainfall, as well as the ability of its shallow roots to suck up as much rain as possible to store in its spongy flesh.  
 
Saguaros have adapted to the Sonoran Desert. They arrived in the region only 8,000 years ago, more recently than humans. Humans living here adapted their lives to include, even revere, the giant cactus. The Tohono O’odham have strong cultural ties to the saguaro. The first saguaro fruit harvest coincides with the Tohono O’odham New Year, when the summer monsoon rains fall on the parched desert floor. The O’odham use woody ribs of dead saguaros to create a tool, called a ku-pit, enabling them to reach the fruit clustered at the tops of the arms and crowns of the cacti.  
 
The timing of the fruit ripening is impressive. Flowers appear in May and June when the desert is at its hottest and driest. The nectar is the only moisture in town, attracting important pollinators like birds and bats. The fruits ripen in July, in time for many animals to eat the delicious red fruits and transport thousands of seeds to new homes. Once the seeds are spread and the monsoon rains start, those seeds have the chance to grow into new giant saguaro. 
 
Even with all of the saguaro’s adaptations to capture and conserve water, without the help of other species it would not survive here at all. It needs animals to pollinate and spread the seeds, and the assistance of other plant species to shelter young seedlings during the first fragile years of their lives. Its appearance as the master of the desert is deceiving. As you travel along what other plants dominate this habitat?