To many people, the word "desert" invokes images of a sun-baked, sand and rock-strewn landscape, where only cacti will grow. While it is true that cacti can be found in all of the worlds' deserts, cacti can also be found in all of the lower forty-eight states. Cacti have evolved from plants that originally grew in more moist environments and exhibit a wide variety of adaptations that have allowed them to exist in the face of changing conditions.
Visitors to the monuments in the Verde Valley will see an assemblage of cacti including species of prickly pear, cholla, and hedgehog cactus. Cacti produce flowers based on the ambient temperature. Ground-hugging species such as hedgehog and prickly pear flower much earlier than the stately saguaro, in part due to the increased temperature at ground level. Cacti are opportunistic plants when it comes to capturing rainfall. Most have shallow taproots, but very well-developed lateral root systems near the surface of the ground that can take advantage of any rain that falls. This can be a disadvantage at times to large cacti, such as the saguaro, in that they can tip over if they engorge with enough water. Cacti not only are efficient at capturing moisture, but have also developed mechanisms to deter any loss of moisture. The prickly pear grows pads at angles that reduce direct exposure to the rays of the sun. Spines also provide limited shade and reduce the desiccating effects of the wind. Spines also deter animals from utilizing the moisture contained within the cactus. Hedgehog cacti will often times be found sheltered at the base of mesquite trees where shade and wind protection is available.
In the Southwest, the prickly pear cactus has a long history of use, from prehistoric times up to the present day. In the spring, the young pads, called "nopalitos", are harvested and eaten before the spines harden. In the late summer, the fruits, called "tunas", are collected and used as picked or serve as the main ingredient in jellies. The pads have been used medicinally in the treatment of burns and cuts, since they contain a mucilaginous substance similar to the mucopolysaccharid hydrogel found between the cells of the body. The polysaccharides help strengthen the hydrogel after it has been damaged