North America has four desert regions. Three are "hot" deserts, including the Mojave, Sonoran and Chihuahuan, which lie in the American southwest. They receive varying amounts of rain -- in late winter in the Mojave, summer in the Chihuahuan, or winter and summer in the Sonoran. They encompass U.S. Department of Agriculture plant hardiness zones ranging from 8a through 10b. The Great Basin Desert, a "cold" desert" in northern Arizona, Utah, much of Colorado and portions of central Oregon and Washington State, receives most of its moisture from winter snow. It encompasses a wider range of USDA zones, from 4a through 9a.
The cooler climates of parts of the Great Basin Desert are well-suited to several different magnolia species. Anise magnolia (Magnolia salicifolia), hardy in USDA zones 4 through 7, grows up to 30 feet tall with smooth gray bark and 4- to 6-inch fragrant white flowers. Cucumber magnolia (Magnolia acuminata), hardy in USDA zones 3 or 4 through 8, grows up to 80 feet tall, with a pyramidal silhouette. The petals are greenish-yellow and appear high in the trees. Many cultivars are sold commercially.
Southern magnolia (Magnolia grandiflora), hardy in USDA zones 7 through 9, is suitable for many parts of the hot deserts as long as its soil is kept uniformly moist. The trees are celebrated for their 8- to 12-inch lemon-scented blooms, which appear in late spring. Growing up to 80 feet tall and 50 feet wide, southern magnolias bear evergreen leaves. Saucer magnolia (Magnolia x soulangiana), hardy in USDA zones 4 through 9, can also survive in hot deserts. It grows up to 25 feet tall and wide and bears tulip-shaped, pinkish buds that open to fragrant flowers.
Always match the magnolia species and variety with your specific desert environment. In hot desert climates, a lightly shaded spot protects the plant from the worst of the sun's rays. Provide supplemental water via drip irrigation during non-rainy seasons, and mulch the magnolia to conserve soil moisture at all times. Magnolias generally bloom in late spring and are probably best suited to desert environments where the majority of the annual precipitation occurs in late winter.