The Mojave Desert covers over 25,000 square miles in parts of southeastern California, Arizona, Nevada and Utah. The Mojave is what is known as a "rainshadow" desert. These are formed when a mountain range (in this case, the Sierra Nevadas) prevents rain clouds from reaching the lee, or protected side of the mountains, forming an area that receives very little moisture. Plants growing here have developed special adaptations in order to absorb or store water.
The Mojave Desert has sparse vegetation, with about 200 endemic (unique) plants not found in neither the Great Basin Desert to the north, nor the Sonoran desert to the south. A number of bushes grow there, but few trees. Although technically it is a yucca, not a tree, the Joshua tree is a well-known exception. Like all desert plants, the plants of the Mojave have evolved so they can survive in an arid environment. Many have a shallow root system, which can quickly absorb rain. Others have spines that serve as a water storage system.
A 2- to 3-foot-high grayish-white shrub, the common saltbush is the dominant plant of the Mojave Desert. It is sometimes mistaken for sagebrush, but is really related to the tumbleweed family. It takes its name from the fact that after it takes up water from the salty desert, it deposits excess salt on its leaves, which helps to attract moisture from the air. It serves as an important source of minerals and food for cattle, deer, pronghorn and desert rodents. It also provides shelter for birds like barn owls and northern harriers.
Another abundant Mojave plant is the 2- to 5-foot-high brittlebush, a member of the sunflower family. It is distinguished by its bright yellow blossoms, which appear from March to June. LIke many other desert plants, it has hairy leaves, which serve as both insulation against extreme temperatures and a way to trap moisture. Growing in dry slopes and basins of the region, brittlebush was used by Native Americans as both a glue and a gum.
The Mojave aster is a small, shrub-like plant, reaching to 30 inches in height, which grows in rocky desert slopes and canyons, according to the Blue Planet Biomes website. It produces long grayish-green stems with narrow, hairy leaves. Each plant bears as many as 20 lavender daisy-type flowers, mostly between March and May. It is a host plant for the Desert Checkerspot, a small orange butterfly with black lines and spots.
This yucca, which grows only in the Mojave Desert, was thought by Mormon pioneers traveling through the region to resemble the Biblical prophet Joshua waving them on to the promised land, according to the Joshua Tree National Park website. Having a height of between 15 to 40 feet and a diameter of 1 to 3 feet, the Joshua tree may live as long as 200 years.
Despite its height, its root system reaches only about 2 feet below ground. The Joshua tree is interesting for its symbiotic relationship with the yucca moth, which has evolved special organs to make it the only creature which can pollinate the tree's flowers. Likewise, the moth relies on the yucca to feed its larvae.