How to Identify Deciduous Trees by Their Leaves

categories of Deciduous leaves for trees illo

Treehugger / Catherine Song

Whether you're on a walk in the woods or a park or merely sitting in your own backyard, you may be curious about the trees around you. Deciduous trees—including oaks, maples, and elms—shed their colorful leaves in the fall and sprout bright new green leaves in the spring. There are dozens of different varieties, each with their own unique leaf structures and shapes.

When identifying leaves, the first thing to look at is the arrangement of the leaves along the stem. Some leaves grow in pairs opposite each other on the stem, while others grow in an alternating pattern.

The next thing to inspect is the structure of the leaves. All leaves consist of two main parts, a petiole and a lamina. The lamina, or the leaf blade, is the flat area where photosynthesis occurs, while the petiole is the stalk that connects the lamina to the stem. If a leaf has an undivided blade, it is classified as a simple leaf. If a leaf has a divided blade—one that forms a collection of leaflets—it is considered a compound leaf.

Compound leaves can be sub-classified based on the arrangement of their leaflets. Palmately compound leaves have leaflets that extend directly from the end of the petiole. They spread out, in sets of three or more, like fingers from the palm of the hand. Pinnately compound leaves have leaflets that extend from a vein that connects to the petiole. Bipinnately compound leaves extend from secondary veins that connect to the main vein.

Once you have narrowed down the type of leaf, you should examine the tree's other features, including its size and shape, its flowers (if it has any), and its bark. Together, this information should allow you to make an identification of the tree.

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Opposite Leaves

Ash tree leaves growing opposite of one another.

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Opposite leaves are just what they sound like: the leaves, whether simple or compound, are located directly across from each other on the same leaf stem. They grow in pairs along the stem.

Examples: Ash, Maple, and Olive.

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Alternate Leaves

Green oak leaves hanging on a tree branch.

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Alternate leaves do not sit directly across from each other on the stem but rather are located in between each other on opposite sides; they grow in a staggered, alternating pattern.

Examples: Hawthorn, Sycamore, Oak, Sassafras, Mulberry, and Dogwood.

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Simple Leaves

Red maple leaves against the sky.

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A simple tree leaf has one blade attached to the stalk.

Examples: Maple, Sycamore, Sweet Gum, and Tulip.

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Compound Leaves

Compound leaves on an Ash tree.

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In a compound leaf, the leaf is divided into leaflets that are attached to a middle vein by their own stalks. If you are not sure if you are looking at a leaf or a leaflet, run your finger down the stalk until you reach the adjoining shoot. The stalk of a simple leaf will end at the point where the petiole joins the stem of the plant. There will be a small bud at this joint. However, there will not be a bud at the base of a leaflet.

Examples: Hickory, Walnut, Ash, Pecan, and Locust.

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Pinnate

Leaves resembling a feather on a black locust tree.

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If compound leaves are alternate in form, they are called pinnate, and they often resemble a feather. There are three types of pinnately alternate leaves: odd, which means there is an odd number of leaflets, with one at the top of the twig; twice pinnate, which means the leaflets are themselves divided into leaflets; and even, which means there is an even number of leaflets on the twig.

Examples: Hickory, Walnut, and Locust.

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Palmate

Close-up image of vibrant, green Horse Chestnut leaves in the spring.

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If compound leaves are opposite in form, they are called palmately compound, and they have a shape that resembles a fan or the palm of a hand.

Examples: Maple and Horse Chestnut.

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Toothed, Lobed, or Entire

Toothed leaves in sunlight.

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Another defining features of a leaf is its margin, or edge. Deeply lobed leaves are easy to recognize, with their obvious protrusions resembling earlobes. Tooth leaves have edges that are sharp and serrated, like a steak knife. Entire leaves are those that have smooth, rounded edges with no defining features.

Within these categories, there is great variation. Some toothed leaves, for example, have clearly defined serrations, while others have much finer serrations resembling a fringe of hair.

Lobed: Maple and Oak.

Toothed: Elm, Chestnut, and Mulberry.

Entire: Magnolia, Dogwood, and Water Oak.