One of the first ways to discover the identity of a tree is by examining its leaves. According to Fairfax County Public Schools, the identity of many trees can be determined just by looking at the shape of a tree leaf. On the other hand, other trees can be are harder to identify, so you need to look for other distinctive traits that can lead to a tree’s identity, such as a tree's leaf arrangement.
The blade of a leaf is the whole leaf unit and sometimes is composed of many smaller leaflets. Leaf margins are the edges of leaves. A leaf base is the term for the portion of the blade closet to the stem. The apex refers to the tip of a leaf. The petiole is the thin stalk connecting the stem to the leaf blade. Stipules are tiny formations at the bottom of the petiole, although sometimes they’re not present, says Pennsylvania State University.
Tree leaves come in various shapes. The leaves of a cabbage palmetto are fan-shaped, notes the Clemson University website. The eastern hemlock has fernlike leaves. The leaf of an alder tree is almost round, according to Schools Liaison. A hazel leaf is also almost round, but has a pointed tip. The shape of a maple tree leaf is three-lobed with wavy edges, while willow leaves are long and thin.
According to North Dakota State University, deciduous leaves are classified into four groups determined by leaf type and arrangement. Simple leaves that grow opposite from each other comprise one group. Common examples are maple and lilac trees. Simple leaves, growing in an alternate arrangement, are a group that includes poplars, birches and willows. Compound leaves found opposite from each other is a third group, in which ash and buckeye trees are included. Compound leaves that grow alternately compose a fourth group that includes walnut and locust trees.
Sometimes determining whether a tree has simple or compound leaves can be tricky, warns Texas A&M. This is because a leaflet can look like a leaf. Whether a leaf is a leaf or a leaflet can be decided by looking for the bud. At the bottom of a single leaf there’s a bud, but there is no bud at the base of a leaflet, notes North Dakota State University.
When determining the species of a conifer tree, count the number of needles on each bundle, known as a fascicle. For example, the white pine tree has five needles per bundle, according to Tree ID. Needles come in pairs on red or Norway pine trees and are 3 to 4 inches long. Tamaracks have bundles of two to five needles per bundle.