Leaves play an important part in the lives of trees because they provide food for trees by turning sunlight into food energy through a process called photosynthesis. They also produce oxygen so humans can breathe. With so many trees, it can seem overwhelming trying to identify a particular species. According to Fairfax County Public Schools, tree identification is simpler than most people realize because a tree's leaves give clues of a tree's identity.
Meanings of Leaf Terms
Knowing the meanings of common leaf terms helps to better understand tree leaves. Leaflets are small or "mini-leaves." The leaflets and the stem make up one entire leaf. The word lobe refers to either the pointed or rounded part of a leaf. The space between lobes is called the sinus. The midvein is the vein that runs down a leaf's center and can be used as a reference point for identifying a tree's species, notes Fairfax County Public Schools.
Trees leaves are considered to be either simple or compound, according to Michigan State University. While a simple leaf is one leaf that has a bud at the bottom of its stem, a compound leaf is made up more than one leaflet or even several leaflets. An example of a tree with compound leaves is the ash tree, which has about five to nine leaflets for each leaf.
Tree leaves come in a a variety of shapes. Some tree leaves, such as those of conifer trees, are needlelike. Other trees have flat broad leaves of various shapes and patterns. An example of a tree with scalelike leaves is the Eastern red cedar. Leaves that are bundled or in clusters include some pine trees such as the Eastern white pine, which has leaves in bundles of five, according to Clemson University. The Virginia pine has twisted leaves that are about only 2 inches long or even shorter.
Tree Leaf Arrangements
There are three main types of tree leaf arrangements, according to Clemson University. Tree leaves can be in an opposite arrangement in which leaves occur in pairs at the nodes. An alternate arrangement is where leaves are located singly at intervals on the stems. A third type is known as a whorled arrangement in which leaves occur in groups of three or more at a single node.
Tree Leaf Diseases
Powdery mildew is a fungal disease in which a powdery white film covers leaves, causing leaves to become distorted. This leaf disease affects leaves of trees such as crepe myrtles and dogwoods. Although powdery mildew can be hard to control, some fungicides are effective, according to East Texas Gardening.
Oak leaf blister is a common spot disease that attacks all types of oak tree leaves. This disease creates spots resembling blisters on leaves, which typically results in leaf distortion. Severe infections can cause some leaves to fall off. Although the leaf spots alone won't kill oaks, leaves falling off prematurely can stress trees.