But what it lacks in size it more than makes up for in numbers. One saguaro produces tens of thousands of seeds in a year, and as many as 40 million in a lifetime of 176 to 200 years. 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.