Saguaro National Park (pics) in Tucson, AZ, comes in two installments, East and West.  The city of Tucson occupies the middle space between the two parts of the park.  The Saguaro, largest cactus in the US grows natively only in the Sonora desert in this part of Arizona.

We visited the west park which is located near the town of Marana, AZ, about 15 miles west of Tucson.  At the visitor’s center one of the park rangers provided a nice overview of the Saguaro cactus plus conducted a walking tour around the visitor’s center to introduce us to the variety of plants that are found in the park.

The Saguaro is essentially a water storage unit.  Its root system is shallow but extends out in a large circle around the base which allows it to soak up whatever water comes its way.  The spines on the Saguaro allow it to expand and contract depending upon how much water it has.  It grows fairly slowly needing its first 10 years to attain a height of 6 inches.  Surprisingly, even with extensive study they have not found any way to reliably determine the age of the adult cacti.  In addition, they don’t know why some grow limbs while others do not, only that generally they are 50 years old before they grow a limb.  The size, shape and configuration of the limbs is highly varied.

In addition to the Saguaro, the Sonora desert has prickly pear, cholla and barrel cacti as well as ocotillo and the palo verde which is the state tree.  We took a hike on Sendero Esperanza which is a trail with about a 700 foot rise in elevation going up to and along the crest of a ridge that runs through the park affording nice views in all directions.