The vastness of Texas means a state containing a large number of different tree species. Identification of many of them is much easier during the months when leaves, flowers or fruit are still on their branches. But when these are absent, you can use other features of the Texas trees to help you identify them.
Leaves are often different from one species to the next, a factor Texas A&M University says will help you greatly in identifying trees. Consider the length, shape, form, apexes, bases and edges of the leaf to come up with a better idea of the species. For example, the leaves on a tree found in the high plains of Texas, common hackberry (Celtis occidentalis), are from 2 inches to 4 inches long, as wide as 2 inches, ovate with long pointed tips, possess a lopsided base and have distinctive teeth along their margins.
Another aspect of the leaves on Texas trees is whether they are simple or compound. Simple leaves consist of a single blade, such as those of American hornbeam (Carpinus caroliniana), a tree of eastern Texas. Compound leaves are more complex, consisting of a rachis (a central axis) with a variable amount of leaflets attached. A Texas example is the pecan (Carya illinoinensis), which has a rachis that can be 20 inches long, with from 11 to 17 leaflets growing from it.
In the winter, when many Texas trees lack foliage, use the bark and the twigs to identify the species. Observe the twigs to determine if they grow opposite each other, alternately on the branches or in a pattern of whorls. Study their flexibility and texture. Look at the bark for its color, texture and appearance. Shagbark hickory (Carya ovata) is identifiable from its grayish bark, which will curl in elongated strips away from the trunk but remain smooth on the branches.
The size of Texas trees often allows you to differentiate between species. You cannot mistake trees of great height for species that seldom exceed 20 feet. First consider if the tree is growing in an ideal habitat for it to achieve its full potential. An American beech tree (Fagus grandifolia) can grow in southeastern Texas to heights of around 100 feet when it receives enough sunlight. But it will be much smaller when developing under the canopy of shade provided by larger trees.
Flowers and Fruit
In the spring, when most Texas trees flower, you can use these blooms to aid your identification. Examination of the flowers of the southern magnolia (Magnolia grandiflora) would reveal a cup-shaped blossom of white that reaches as far across as 8 inches. The flower will be aromatic and possess blotches of purple in its middle. As the flowers develop into fruit, you can use its appearance to confirm your identification. You would see southern magnolia's flowers change during the summer into what the "National Audubon Society Field Guide to Trees" calls a "conelike" collection of pods that split open in fall to reveal brilliant red seeds.