Arizona lies in USDA Hardiness Zones 5 through 10 due to the fact that there is a wide discrepancy in elevation from the flat lands of the desert to the mountains. Arizona has shade trees that can adapt to the different conditions and are very unique to the Southwest.
Chinese elm (Ulmus parvifolia) is also known as lancebark elm. The tree grows up to 50 feet with about the same spread. The dark-green leaves grow to about 2 inches long and 1 inch wide with tiny hairs on the underside and turn a yellow-brown in the fall. Small green-red fruits appear in the fall. Plant Chinese elm in full sun and a moist, well-drained soil. The tree is resistant to Dutch Elm Disease, a condition that can wipe out other elm species. In Arizona, Chinese elm is hardy in USDA Zones 5 through 9.
Texas Red Oak
Texas red oak (Quercus buckleyi) is also known as Buckley oak, Spanish oak, spotted oak and rock oak and is a member of the beech family. The tree grows up to 50 feet tall with dark-green elliptic or oval leaves that grow up to 5 inches long and 4 inches wide and turn brown or red in the fall. The small red flowers bloom in April, May and June and are followed by egg-shaped acorns that remain on the tree for two years. Plant Texas red oak in full sun or partial shade and a loam or clay soil that is dry. The tree is hardy in USDA Zones 7 to 9 in Arizona and small animals will come for a meal of the acorns.
Honey mesquite (Prosopis glandulosa) is a member of the pea family that grows up to 30 feet tall with a crown spread that is equal to or greater than the height. The tree features twigs that are covered with 2-inch long thorns and bright-green, feathery leaves. The yellow-green flowers bloom from April through August and are followed by a long yellow-brown seed pod. Plant honey mesquite in full sun and a dry sandy, loam or clay dry soil. Bees and butterflies will stop by for the nectar and birds will make a meal out of the seeds. Honey mesquite is hardy in USDA Zones 6 through 10 in Arizona.
Incense cedar (Calocedrus decurrens) is an evergreen tree that grows from 30 to 150 feet tall with a trunk that grows as much as 6 feet in diameter. The leaves are short, flat and over-lap each other lying close to the branches. The tree will have both male and female cones growing on separate branches. Plant incense cedar in full sun or partial shade and a soil that is very moist and well drained. The tree is hardy in USDA Zones 6 through 8 in Arizona.