I'm always asking the guests I ride with how much they know about the alien looking Saguaro cactus. And the answer is often "nothing" which I think is sad because they are a wonderful, interesting plant.
Their Latin name is Carnegiea Gigantica.
Their average life span is 150-175 years.
They typically grow between seal level and 4000 feet in the areas of the Sonoran Desert where freezing temperatures are minimal.
They are very slow growing - only about 1 -1.5 inches in the first 8 years of their life. They begin growing under what is know as a "nurse tree" (Ironwoods, Palo Verdes, Mesquites).
Branches/Arms do not begin to grow on a Saguaro until it is 50-75 years old. this does, however, depend on the amount of water the Saguaro is receiving.
The roots of a Saguaro are very shallow to allow it to absorb as much water as possible. After a period of rain the Saguaro will expand and look fatter - the pleats that make up its body store the water and swell. After a dry spell the Saguaro will look thinner having used up a lot of its water stores.
Sometimes there are holes in the Saguaros typically created by the Gila Woodpecker. When the Woodpecker moves out of its nest hole other birds such as Sparrows and Elf Owls will move in. Larger birds such as Harris Hawks and Red Tails will build their nests on the outside when the arm meets the trunk of the Saguaro.
We think they are amazing.