Glance at a tree and you no doubt first look at its leaves. There are all sorts of interesting shapes and sizes, and often people will learn to recognize a species based on its leaf fingerprint. Other times, you can recognize a tree by its flowers.

But you can also identify trees by looking at their bark. At first glance, this protective outer coating of a tree's trunk and branches may seem like an unending sea of gray and brown. However, when you look closely, you'll see variations in the colors and textures.

"If you want to experience a forest, mingle among its trees," writes Michael Wojtech in the preface to his book, "Bark: A Field Guide to Trees of the Northeast."

"If you want to know the trees, learn their bark."

There are various patterns, textures and other characteristics of bark that can help you identify trees without a single glance at its leaves or needles. Here are some ideas to get you started.

Smooth, unbroken bark

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Young trees sometimes have smooth bark that's unbroken by ridges. Often this will change as the trees age, Wojtech says. But a few species, like the American beech and the red maple, keep their smooth, unbroken bark throughout their lifespans.

Bark peeling in horizontal strips

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Sometimes you'll notice that a tree's bark might be peeling.

In some cases, Wojtech says, the trees' wood is growing faster than the bark surrounding it, so it pushes outward against the bark. On some species, the pressure causes thin layers of the protective outer cork layer to separate and peel away. In the paper birch, for example, these layers peel away in horizontal, curly strips.

Lots of lenticels

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Lenticels are pores that are important in the process of moving carbon dioxide and oxygen through a tree's protective outer bark. All trees have them, but they're more visible on some species than others, according to Iowa State University Extension and Outreach.

Lenticels come in many different shapes, sizes and even colors. For example, Wojtech points out that they appear as dark, horizontal lines in the yellow birch and as diamond shapes in the young bigtooth aspen.

Deep ridges and furrows

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If a tree has very rough bark, take a look at its ridges and furrows. These are actually gaps in the bark's outer layers, called the rhytidome.

Some species, like a white ash, can have ridges and furrows that intersect. Others, like the Northern red oak above, have uninterrupted ridges. The white oak has ridges that are broken horizontally.

Scales and plates

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Instead of ridges, some trees have breaks in the rhytidome layers that appear more like plates or scales. Many pine and spruce trees have scales of bark, while species like the black birch have thick, irregular plates on their trunks.

Rainbow of colors

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It's not just the texture of the bark that helps identify the tree, but the color as well. Although at first glance, trees may seem like an interchangeable mix of muted grays and browns, there's more to that forest rainbow.

As Hunker points out, "Beech trees have a light gray bark, and cherry trees have a red-brown bark. Black walnut trees have very dark bark, while birch trees have white or silvery bark."

Unusual characteristics

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Aside from ridges and lenticels, color and peeling layers, some tree species just have some strange things growing on their bark.

For example, wild varieties of the honey locust tree have large, red thorns on the trunk and branches. The thorns usually have three points, but can have many more, especially on the trunk. They look like spines and can grow to be three inches long.

Similarly, the Hercules club (also known as the toothache tree) grows wart-like tubercles on its bark.

Smell test

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One more way to identify a tree is by taking a whiff of its bark. The National Park Service points out that you can recognize some trees by smelling their bark. The Ponderosa pine, above, for example, smells like butterscotch or vanilla.

Hunker says some other pine trees smell like turpentine, while yellow birch smells like wintergreen, and sassafras trees can smell like cinnamon and spice.

So the next time you're out in nature, take a closer look at the trees around you. You might see more details in the different tree barks than you ever have before.