The first trip was to West Saguaro NP. West and East Saguaro National Park sit like bookends on either side of the city. The West side seemed to have more of what we wanted to visit.
It made me think of a forest – if there is such a thing as a Cactus Forest.
A Ranger recommended that we might like to try the Signal Hill Trail that led up to some interesting petroglyphs (Rock Art) and a great panoramic view.
The area was developed by the Civilian Conservation Corp (CCC) who were FDR’s answer to unemployment during the Depression of the 1930s.
Corps of men were fed, educate, housed and paid $1.00 per day (75% of which was sent back to their families) in exchange for developing the various national sites.
They think that the petroglyphs were left by the Hohokam people thousands of years ago. There is little know about these people or the rock art that they left behind but it is probably akin to the graffiti of today.
The Saguaro Cactus is fascinating – from it’s humble beginning to its haunting shape that’s become a symbol of the desert for me.
The Saguaro can only propagate from seed and under specific conditions. It is very sensitive to frost and wind and needs heat and moisture. The Saguaro is found only in the Sonora Desert.
The cactus usually begins life being sheltered by a "nurse" tree or shrub (a Creosote, Mesquite or Palo Verde) that provides shade and moisture to help it grow. So you often see the Saguaro surrounded by bushes.
Eventually the cactus takes most of the nutrition and the nurse plant dies.
The Saguaro grows very slowly –maybe an inch a year - but to a height of 15 to 50 feet. The largest plants, with more than 5 arms, are estimated to be 200 years old. An average old Saguaro would have 5 arms and be about 30 feet tall. The one in this photo has 7 arms and we’ve seen cactus with a whole lot more.
Prickly spines run vertically along the entire length of the cactus. After a heavy desert rain, the spines are further apart when the cactus swells by absorbing the moisture. As the desert dries out, the spines come closer together,
It’s almost impossible to find a Saguaro that has no damage. Birds (particularly the cactus wren) build their nests time and time again in small holes in the cactus. Once there is a nest there, the cactus develops a kind of callus around it to conserve the moisture and protect itself. This callus is what they call a boot.
I’m not sure if you would call it an injury, but a crest can develop on the top or between the arms of the Saguaro. A friend of ours (Sheila) has a list of highway mile markers where she has seen the crested Saguaro.
The question that puzzles me the most is: What triggers the growth of an arm? Every time I ask, I get a different answer: when the rains are heavy, the arms allow the cactus to absorb more moisture for when there is a drought; because the Saguaro only propagate by seed, more arms develop when the plant seems threatened; and finally, why do other trees produce their branches? Interesting, eh?
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