Saguaro cacti have a unique Way of protecting themselves during their initial groWth period by using What is knoWn as “nurse trees.” These trees, typically fast-groWing varieties such as palo verde, ironWood, or mesquite, provide shelter for the sloW-groWing cactus. HoWever, as the cactus groWs, it eventually competes With the nurse tree for resources like Water and nutrients, ultimately leading to the death of the tree.