Desert plants include cactus, unicorn plant, desert lily, western peppergrass, turtleback, paperflower, century plant, blue palo verde, desert mariposa tulip, desert sand verbena, sagebrush, creosote bush and pale trumpets. Desert plants are well-adapted to grow in climates where precipitation is scarce and temperatures may be extreme.
Cacti have adapted exceptionally well to desert conditions. Over time they have changed their shape so that their external surface is reduced in relation to their volume. They've gotten rid of green leaves and let their stems handle photosynthesis. In many types of cactus, the stems have become round or flat. Prickly pears orient themselves so that the flat sides of their stems face east and west. In this way, the worst heat of the midday sun only strikes the edges of the stems.
Cacti have also evolved to efficiently collect and conserve water. Young cacti have spines that point downward. Spines are modified leaves that keep the plant cool by absorbing and reflecting light. They also offer the plant protection. The spines on these cacti collect dew, fog and other precipitation and channel it to the plant's roots.
Spines, thorns and bristles are not just found on cacti. Agaves such as the century plant can have sharp spines.