In late April through early June, the tops of the saguaro's trunk and arms sprout a profusion of large, creamy white flowers. Individual flowers open at night and close the following afternoon. To develop into fruits, they must be pollinated within this time frame. Pollination is carried out by nectar feeding bats, birds and insects.
How Saguaros Reproduce
Each fruit contains about 2,000 tiny black seeds. When the fruit and seeds are eaten by a coyote or cactus wren, the seeds pass through their digestive system unharmed and are distributed throughout the desert. However, if the seeds are eaten by a dove or quail, they will be completely consumed in the digestive system.
It is estimated that a saguaro can produce some 40 million seeds during its lifetime. However, few will survive to become a seedling. Fewer still will become an adult. The low survival rate of seedlings can be attributed to drought, prolonged freezing, or animals eating them.