Identify the different trees of Ohio when their leaves are on them. Direct your efforts on such characteristics of the leaves as their size, their contours, their summer and fall colors and their arrangement on the branches. Concentrate on whether the leaves are simple, meaning the leaf is a single blade, or if the leaves of a particular specimen are compound, or composed of three or more smaller leaflets arranged on a long stem. Remember that other features of the leaves on Ohio's trees make it possible for you to render an identification of the tree by studying them.
Look at the leaves and distinguish which are compound leaves like those of the hickories and ashes. The trees with compound leaves will have branches full of long stems upon which these leaves exist, carrying multiple smaller leaflets arranged in different positions depending on the species. The state tree of Ohio, the buckeye, has palmately compound leaves, a term describing leaflets that attach at the end of a leaf stalk, arranged like fingers on a hand or the many spokes of a wheel.
Count the leaflets on the stems of species with compound leaves to aid in identifying the tree. Shagbark hickory, for example, typically has five separate leaflets on one leaf stem. Green ash has between five and nine leaflets.
Measure the size of the leaves of Ohio's trees to determine what type of tree features them. Some are very large, like those of the northern catalpa, which approach a foot in length. Note that others, like those of some of the state's birches, are as small as 2 inches long.
Examine the different shapes of these leaves to come to a positive identification of a species. Consider if the leaf is elliptical, oval, rounded, or irregular in shape. Remember that some leaves have the ability to identify their tree by their shape alone, such as the tuliptree. This Ohio tree has leaves with the shape of the outline of a tulip flower, which quickly gives away what kind of tree upon which they grow.
Inspect the leaves for their colors, looking at both the upper surface of the leaf and the lower surface. Notice that in many instances, there are subtle and sometimes not-so-subtle differences in the shades on these two surfaces. Look closely at a silver maple and you will see the tops of the leaves are a dark green but the underside of the leaf is a silvery color.
Investigate the autumn colors of the Ohio trees, which can help immensely to reveal the tree's identity. Scrutinize the countryside, looking for trees that feature outstanding hues like red, orange and yellow. In Ohio, these will often be maples, scarlet oaks or aspens. Look for leaves with brown or dull yellow colors, which are typically oaks, hophornbeams and beeches.