Many people associate the desert area of the southwestern United States with extreme heat and little to no water. However, plenty of plants have adapted to the harsh environment and will not only survive but thrive--even producing flowers and food in the process. Plants that survive in the desert do so by conserving water, storing water and reducing heat input, among other conservation techniques.
Cactus and Succulents
Cactus plants and other succulents, such as aloe vera and agave, survive in the desert by storing massive amounts of water as quickly as they can when it rains. Their root systems are shallow and spread wide so that when it rains, the water can be absorbed from the soil's surface before it evaporates.
Cactus and succulents also have very thick, waxy skin that helps them seal in moisture instead of letting it evaporate into the air. These types of plants also tend to breathe through their pores at nighttime when it's cooler, and close the pores up during the hottest parts of the day when water loss can occur faster.
Most cactus plants produce unusual looking flowers in reds, yellows, oranges and purples, making them attractive and desirable even in home desert gardens.
Besides cactus and succulents, there are a wide variety of annual and perennial wildflowers that survive naturally in the desert. Most desert wildflowers have light-colored stems and leaves--gray-green or gray-blue in color--and less foliage than flowers and plants that grow in water-rich areas. The lower amount of foliage means there is less parts of the plant to supply water to, and the lighter colors help naturally reflect some of the sun's heat.
It's also common to see plant leaves that stand upright instead of spreading out horizontally. This vertical orientation helps the plant protect itself from the heat of the sun by reducing the surface area the sun can reach.
Some annuals and perennials survive in the desert simply by modifying their growing and blooming season to avoid the hottest and driest times of the year. Prolific wildflowers that survive in the California and Arizona deserts include the California poppy, desert mallow, and desert sand verbena.
Trees and Shrubs
Trees and shrubs that survive in the desert usually do so by sending a deep tap root into the ground that provides them with access to underground sources of water.
Mesquite trees are one such desert shrub that develops a very long tap root, some of which have been discovered to be 80 feet long. The Creosote bush also utilizes deep tap roots to access underground water, but it's unique in that it also uses several other desert survival techniques. It has a radial root system that allows it to absorb surface water when it rains, plus it closes its pores during the day and opens them at night.