One saguaro produces tens of thousands of seeds in one year, and as many as 40 million in a lifetime of 175 to 200 years . But from the start the odds against survival are great. Out of all the seeds that one saguaro produces in its life, probably only one will live 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.
Saguaros do best on bajadas gently sloping outwash plains at the foot of desert mountains.
Growth of a Green Giant A saguaro's growth is extremely slow. Growth occurs in spurts, with most of it taking place in the summer rainy season each year. By the end of a year the saguaro seedling may measure only 14 inch. After 15 years, the saguaro may be barely one foot tall. By 50 years the saguaro can be as tall as seven feet.