Montezuma Castle National Monument - Cacti / Desert Succulents

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 most 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 temperatures at ground level. Cacti are opportunistic plants when it comes to capturing rainfall and minimizing water loss. Most cacti 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 that allow the plant to reduce water loss. Most cacti have a tough, waxy outer layer that deters moisture loss. Some species of cacti open their pores only during the cooler, more humid nighttime hours. The prickly pear grows pads at angles that reduce direct exposure to the suns rays. Spines provide limited shade and reduce the dessicating effects of the wind. Spines also deter most animals from utilizing the water stored in the plants tissues. 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 by the native inhabitants 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 eaten 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 mucilagenous substance similar to the mucopolysaccharide hydrogel found between the cells of the body. The polysaccharides help strengthen the hydrogel after it has been damaged.