Shade is essential in the Desert Southwest. As a result, Arizona residents often plant lots of trees to augment the native species growing in the state. Drought-tolerant trees that provide shade, as well as fuel, food and shelter, are especially prized.
There are literally hundreds of different species of trees native to Arizona and hundreds that have been introduced. The Australian bottle tree, Canary Island date palm, Chinese elm, Chilean mesquite tree, Chinese pistache and the Australian coolibah tree are but a few of the foreign trees now commonly found growing in Arizona.
There are also many different varieties of citrus trees that have been introduced to Arizona. Common citrus trees include lemon, orange, tangerine, grapefruit and lime. Citrus grows well in lower-Arizona desert locations.
Examine the tree's location and growing conditions. Determine if it is a planted landscape tree or is growing wild. Make note of the amount of sunshine the tree receives and its proximity to a water source, stream or lake bed.
Look at the size of the tree. Some trees reach giant heights at maturity, while others may never exceed 10 feet in height.
For example, the Afghan pine tree (Pinus eldarica) is commonly sold in Arizona as a living "Christmas tree" and is then replanted in urban and rural landscapes. It grows to heights of 30 or 40 feet.
Look at the tree's leaves. Leaf shape, size, color and texture help in tree identification. Leaves may be heart-shaped, round, oblong, oval, wide or narrow. Some leaves have smooth edges; others are rippled or toothed.
The Discover Life website offers a tree identification guide on which you can enter specific tree leaf shapes, as well as other distinctive characteristics you have observed. By clicking on certain shapes and boxes, you will be provided with the tree's type or name.
Visit the University of Arizona's Campus Arboretum to view some of Arizona's rarest and most unusual trees. The campus boasts several exotic trees that come from as far away as Argentina, Africa and Brazil. The arboretum also features several trees native to Arizona. Alternatively, the arboretum's trees can be viewed online.
Arizona is justifiably proud of some of the spectacular trees found throughout the state. Several are listed in the "United States Register of National Trees." As of 2005, 88 Arizona trees have been honored. Twelve were introduced to the state, while the remaining 67 are native to the state.
Take a sample of a twig and leaf from the tree. Consult your local county extension agent. A trained tree specialist is familiar with the trees that are native to your area and can provide identification and information on their care and cultivation.
Research Arizona trees online at the Arbor Day Foundation website, which offers an interactive tree data base and several tree identification books for purchase. Tree identification guide books are also available at the public library or from local book stores.