From the start, the odds against survival are great. Out of all the seeds that a saguaro produces in its life, probably only one will survive to adulthood. Saguaro seedlings that grow under these sheltering plants are shaded from the desert's intense sunlight, blanketed from winter cold, and hidden from rodents, birds, and other animals that eat them. Rocks provide similar protection for young saguaros. A saguaro's growth is extremely slow.
Growth occurs in spurts, with most of it taking place in the summer rainy season each year.
After 15 years, the saguaro may be barely a foot tall. At about 30 years saguaros begin to flower and produce fruit. By 50 years the saguaro can be as tall as 7 feet. The branches begin as prickly balls, then extend out and upward. By 100 years the saguaro may have reached 25 feet.