teacher's lounge
The Natural History of the Saguaro Cactus
The desert is a fragile and delicate environment. It is shaped by climactic extremes. Rainfall is unpredictable and sparse at best. Water is difficult to find in large supply. The desert may appear lifeless, but within its parched environment are intricate living systems, each fragment performing a slightly different function and each fragment depending on the whole system for survival. No place is this more apparent than in the Sonora Desert of the American Southwest. Since the beginning of the last century people recognized the fragility of this landscape and in 1933 a Saguaro National Monument was created. The Saguaro Wilderness Area of 71,400 acres was added in 1975. Saguaro National Park was created from these areas in 1994 and currently encompasses 91,327 acres in it's two districts.
For centuries, peoples of the Sonora Desert have been using natural products of the saguaro cactus. Native Americans used the fruit for jam, syrup and religious ceremonies. The fruit was so important that for some groups, its harvest marked the beginning of the new year. Seeds were also harvested. Wood provided strong materials for fences and shelters.
The saguaro is a very slow growing plant. It begins its life as a black seed smaller than a pin head. A single saguaro cactus can produces as many as 40 million seeds in a lifetime. Few survive to adulthood. Studies indicate that saguaros only grow between 1 and 1 ½ inches in their first eight years of life. Growing under the protection of a mesquite or Palo Verde tree the saguaro does not produce its first flowers for 35 years and may not grow its first arms for 50-70 years. A saguaro is considered an adult when it reaches 125 years old. It may weigh 6 tons. Some biologists believe the saguaro can live to be 200 years old.
The saguaro is home to a variety of animals including woodpeckers that excavate nests in the cacti’s pulpy flesh. Other birds take up residence in these cavities when they are abandoned by the woodpeckers. The cactus also provides food for animals. Bats drink the flower nectar and in turn pollinate the flowers. Birds, bats, mammals, reptiles and insects all feast on the fruit provided by the saguaro in mid-summer. When water sources are not available, pack rats, jackrabbits, mule deer, and big horn sheep will eat the young flesh of the cactus.
There are many threats to the saguaro cactus. The heat of the desert, animals, fire, the introduction of exotic plants, and an ever- expanding human population all threaten the survival of this American icon. Another threat is theft. The saguaro is one of many plants in Arizona’s Saguaro National Park that is protected by the Native Plant Protection Act. The removal of the plant is illegal.