Saguaro produce creamy-white, 3-inch-wide flowers with yellow centers which bloom in May and June and their juicy red fruit matures by late June. Their blossoms open during the cooler desert nights and close again by noon the next day. Saguaro flowers are pollinated when birds, bats and insects are attracted by their sweet nectar. The Whitewing Dove is one of the saguaro’s primary pollinators. The Gila Woodpecker and the Gilded Flicker build their homes in the Saguaro Cactus by chiseling out small holes in their trunks. The Saguaro blossom is the state flower of Arizona.
In contrast to their giant adult size, saguaro spring up from tiny, black seeds. Saguaro flowers are capable of producing tens of thousands of seeds a year, during a lifetime that may span from 175 to 200 years. However, only a small percentage of the seeds produced actually survive, grow and become adult saguaros.
Many Saguaros do not live to die of old age. In spite of their great size, they are vulnerable during every stage of their lives. Many die annually due to extreme temperatures, lightning, wind or severe droughts. Others are impacted by human threats, such as pollution and cactus rustling - when they are stolen for landscaping use. Livestock grazing, which lasted from the 1880's until 1979, devastated some cactus forests. Their survival is also threatened by animals, who eat their seeds and seedlings.
A saguaro’s growth cycle is very slow. Their chances of survival are improved if they have the luck to spring up near the shelter of nurse trees, such as palo verde and mesquite, or near rocks which can provide them with protection from the desert's intense sunlight. The ideal environment in which saguaros can survive and thrive are on rocky bajadas, which are gently sloping outwash plains at the foot of desert mountains.
With a slow growth pattern, Saguaros may only reach a foot in height after 15 years. Most of their growth occurs during the summer rainy season. They begin to flower and produce fruits after about 30 years, and by the time they are 50 years old, their height may reach seven feet. At the age of 75, they begin to grow branches or arms, that eventually extend outward and upward. Saguaro’s can grow to 25 feet tall by the time they reach the age of 100 years old and attain a height of 50 feet by the age of 150.
In spite of all the challenges to their existence, there is a resurgence of saguaro growth in some areas today, where thousands of young saguaros have taken hold and are thriving - lending their centuries-old dignity to the Arizona landscape.
Information for this story was gathered from web sources, including information from the National Park Service.