The trees in the desert settings in the United States and into Mexico have an array of leaves. Identification of these desert tree leaves is a bit simpler than trying to identify leaves of trees in other ecosystems. This is because fewer trees live in the desert, with the number of species that adapted to the dry conditions limited.
Types of Leaves
You may see many types of leaves in the trees of the desert. Among them are the simple leaves of the Rio Grande cottonwood, composed of a single blade. Compound leaves comprising one or more axils containing numerous small leaflets are also present on some desert trees, most notably the mesquites. Larger leaves of this nature are on the California fan palm, with the leafstalk containing fronds arranged in a fan shape.
Shape of leaves or leaflets plays an important role in the identification of desert tree leaves. Using shape is a quick way to identify the foliage on a desert willow, for example. The leaves of this tree are slender, pointed and elongated in the same manner as those of many willow varieties, despite the fact that this is not a relative to North American willows. Several kinds of desert trees possess unique leaf shapes, including the Joshua tree, a spike-leafed evergreen.
Leaf Time Frames
The period during which leaves occur on some desert tree species can allow you to pinpoint the type of tree by its leaf. The foliage on a smoke tree is fleeting, coming in during the spring but lasting only a few weeks, until the flowers develop. Other leaves are evergreen, remaining on the branches until their replacements grow in, such as the California fan palm.
Using Leaf Colors
Sometimes color of leaves or leaflets can differentiate species in the desert. The Southwest is home to three kinds of mesquite tree; these three varieties are the most common trees in the desert regions in America. To distinguish the leaves from one another, look closely at the color of the numerous leaflets that make up these compound leaves. Those of honey mesquite are yellow-green, the leaflets of screwbean mesquite are a duller shade of plain green and the leaflets on a velvet mesquite are dull green but covered with fine gray hairs.
You may find that while trying to identify the leaves of certain desert tree species that some trees will drop their foliage long before winter. This often occurs in response to cool weather or severe drought. Trees such as the Palo Verde tree will shed leaves and leaf stems to conserve water in times of very dry conditions but can still photosynthesize to remain alive, with the process accomplished by its green bark.