Identify a Tree Using Leaf Shape, Margin, and Venation

Leaf shapes play an important role in tree identification, providing key characteristics that botanists and foresters rely on. As a result, botanists and foresters have developed terms for the patterns and shapes used in tree identification, and many of those terms are used when observing a tree's leaves.

Some tree species display more than one type of leaf structure, while other trees clearly display the same leaf structure throughout. Trees with especially unique leaves include ginkgo, sassafras, yellow poplar, and mulberry.

Here, we explore the various classifications that foresters study when identifying trees by leaf shapes.

Leaf Shape and Arrangement

Studying leaf shape and the arrangement of leaves on a stem is the most common way of identifying a tree in the field during the growing season. The novice taxonomist usually starts with a tree leaf shape, which is determined by the presence or absence of lobes. Sometimes, it is possible to name the tree species without using any other identification marker.

A tree's leaves can also vary in shape according to their position on the tree, their age after budding, and the presence or absence of insect or disease damage. These variations are usually easy to deal with by finding a healthy specimen in its natural environment.

• Leaf shape can vary considerably. The most common shapes include oval, truncate, elliptical, lanceolate, and linear. Leaf tips and bases may also be unique, with names based on their shapes.
• Leaf arrangement is mainly limited to two basic petiole attachments: simple and compound. Compound leaves are further described as pinnately, palmately, and doubly compound.

Leaf Edges or Margins

All tree leaves exhibit margins—the blade-like edges of the leaves—that are either serrated or smooth. Leaf margins can be finely classified based on at least a dozen unique characteristics. There are four major classifications into which all others fit:

• Entire Leaf: The margin is even and smooth around the entire leaf edge. Examples are magnolia or dogwood tree leaves.
• Toothed or Serrated Leaf: The margin has a series of toothlike pointed teeth around the entire leaf edge. Examples are elm and mulberry tree leaves.
• Lobed Leaf: The margin has an indention or indentions that go less than halfway to the leaf midrib or midline. Maple and oak trees have lobed leaves.
• Parted Leaf: The margin has an indention or indentions that go more than halfway to the leaf midrib or midline.

Leaf Veins and Venation Patterns

Leaves have unique structures, called veins, that transport liquids and nutrients to leaf cells. Veins also carry the products of photosynthesis back to the rest of the tree.

A tree leaf has several types of veins. The central one is called the midrib or midvein. Other veins connect to the midrib and have their own unique patterns.

Tree leaf veins in dicots, also known as hardwoods or deciduous trees, are all considered to be net-veined or reticulate-veined. This means that the veins branch from the main rib and then sub-branch into finer veins.

There are two classifications you need to know for tree identification:

• Pinnate Venation: The veins extend from the midrib to the leaf margin. Oak and cherry tree leaves have pinnate venation.
• Palmate Venation: The veins radiate in a fan shape from the leaf petiole. Examples include maple and sweetgum leaves.