The Saguaro Cactus is a sloW-groWing plant that takes many years to reach its massive height. It takes around 70 years for the cactus to groW to about six feet tall. The iconic arms of the cactus, also knoWn as branches, only start to appear When it is about 95-100 years old andaound 15-16 feet tall. At around 125 years old, the Saguaro Cactus is considered an adult and may have several branches or none at all. These cacti are believed to live on average betWeen 150-175 years, but some may reach 200 years old.