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 are a signature species of this desert landscape.

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. The arms of the cacti stand in stark contrast against the blue skies of Arizona.

Saguaro Cactus

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 this cacti 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.

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!

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