In the past, people have asked me how long does a saguaro cactus arm take to grow back. The commonly held belief is that it takes 100 years before they will develop an arm.
However, as with much plant information, this answer is not always correct, it actually takes less time for a saguaro cactus to grow its arm back in a landscape setting than it’s native habitat.
The most critical factor in determining the timing of when a saguaro will start to grow an arm is the availability of water. Put simply, the more water a saguaro receives, the more quickly it grows. In a landscape setting where irrigation is present, a saguaro will grow much more rapidly then they do in their natural desert habitat. Saguaro cacti that grow in southern Arizona (near Tucson) grow more quickly than those in the western areas of the Sonoran desert because there is more rainfall in southern Arizona.