Simply Saguaro – Arizona SkyWatch #7

It’s a dark, wet, rainy night here on Vancouver Island so my thoughts turn southward once again to the blue skies of Arizona for SkyWatch Friday inspiration.

Saguaro Cactus (Carnegiea gigantea)
Saguaro Cactus (Carnegiea gigantea) with arms reaching to the sky.

Last March I traveled with two other naturalists to Arizona for a week of botanizing and birdwatching. One of the National Parks we visited was Saguaro National Park near Tucson, Arizona. The Sonoran Desert here is dominated by Saguaro Cacti (Carnegiea gigantea) and for a “wet coaster” the landscape is dramatic.

Saguaro Cactus (Carnegiea gigantea)
Saguaro Cactus (Carnegiea gigantea) growing in association with a nurse tree.

Saguaros are a very slow growing cacti – in the first eight years of their life they may grow between 2.5 to 4 cm. Often they start under a nurse tree, typically a palo verde, ironwood, or mesquite tree. Growth rate is dependent on climate, precipitation, and location. Generally the first branches of a Saguaro appear when the cactus is between 50 and 70 years of age. The average lifespan of a Saguaro is 150 years but some may live up to 200 years.

Saguaro Cactus (Carnegiea gigantea)
Pleats of the Saguaro Cactus (Carnegiea gigantea). These expand like an accordion when the cactus absorbs water.

Saguaros are pleated so that they can expand during periods of heavy rainfall and absorb the extra water. As the cactus uses up its stored water the pleats contract. Long woody ribs inside the Saguaro help to support the enormous weight of water inside the cactus. An adult plant (125 years +) can weigh up to 6 tons!

Saguaro Cactus (Carnegiea gigantea)
Saguaro Cactus (Carnegiea gigantea) spines - ouch!

Memories of blue skies and very cool cacti – a fitting subject for SkyWatch Friday. See more beautiful skies at:

SkyWatch Friday


  1. Thanks Bill – every now and then I post about a nature related trip beyond BC and this is one of them. Saguaro probably wouldn’t do too well on Vancouver Island but we do have a small Brittle Prickly Pear (Opuntia fragilis) that grows on the Gulf Islands between Vancouver Island and the mainland. Thanks for stopping in!

  2. Your weather is wet and rainy; mine is cold and gray and snowy. How wonderful to remember the warm sun and brilliant blue skies of Arizona. Last April I was in Phoenix and was able to go to the Desert Botanical Garden. This was during a major Chilhuly installation and was magnificent.

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