Once you can identify your local trees by their leaves, flowers and fruits, here's a fun thing to do: Learn to identify them strictly by their bark. This is something you can do in the wintertime, too.

Some tree trunks are painfully easy to identify. That's the case with the tree at the left, the Honeylocust, Gleditsia triacanthos. The trunk of no other tree in eastern North America bears such large, branched thorns as this species. Those spines can be three inches long and longer (8 cm) and I've had them go right through the sole of my shoe, deep into my poor foot!

The trunk at the left also is pretty unmistakable. Those half-inch-high, cone-shaped spines are on the Hercules-club tree, also known as the Toothache-tree, Zanthoxylum clava-herculis. These spines make more sense when you remember that when the tree evolved large grazing animals roamed the land and they could nibble a defenseless tree to a nub in no time.

In contrast to the two above barks, the shallowly and irregularly furrowed bark at the left, of the Sweetgum tree, Liquidambar styraciflua, is about as "average" as a tree bark can get. In fact, it can serve us as our "Standard Bark." When we learn new barks, we can get their characteristics fixed in our heads by noticing how they are different from the Sweetgum's.

Notice these "average" features about the Sweetgum's bark:

• it is grayish, not very dark, not very light
• ridges between fissures are flat, narrow and irregularly formed
• fissures are neither very shallow nor very deep

Now let's look at other trunks to see how they differ from our "standard trunk," the Sweetgum's.

That's a Black Walnut, Juglans nigra, trunk at the right. It's different from the Sweetgum's "average trunk" by being strongly furrowed and blackish. Notice how the ridges, or furrows, between the fissures are sharp or broadly rounded. Not many trunks are so dark and deeply fissured, so this is a fairly easy bark to learn.

The picture at the left shows the dark reddish brown, rough, scaly plates of the Longleaf Pine, Pinus palustris. Several but by no means all pines have barks similar to this. You can walk up to some of them and peel thin flakes like pieces of stiff posterboard off the plates. If you get that close to the trunk, another identification feature of pine trunks becomes noticeable -- they smell like turpentine!

This trunk at the right belongs to a Persimmon tree, Diospyros virginiana. It's also blackish and also deeply fissured, but instead of vertical ridges running up and down the trunk, the bark is composed of more or less  rectangular blocks. This trunk doesn't fit any of our "basic bark types." In real life, Persimmon bark is blackish, too, not gray, but that doesn't show up so well in the picture. Actually, Persimmon bark is one of the easiest barks to recognize because of its blocky character, the deep fissures, and the blackish color.

At the left is the smooth but blotchy bark of the Crape Myrtle, Lagerstroemia indica.

The bark at the right is of a Yellow Poplar, or Tuliptree, Liriodendron tulipifera. Like the Sweetgum's trunk, its bark is grayish and has fissures, but it's obviously a bit different from the Sweetgum. First of all, let's notice that it's sort of blotchy. It has large gray blotches on a grayish-brown background. Well, the gray is lichen, so this is something you need to look out for. A Yellow Poplar's bark is usually considered to be gray-brown. Also, notice the series of holes in more or less horizontal lines across the bark -- a close-up is shown at the right. These are holes made by the woodpecker known as the Yellow-bellied Sapsucker. The sapsucker drills the holes, then drinks the sweet sap that runs out. Therefore, don't expect all Yellow Poplar trunks to bear sapsucker holes! Removing the algae and the sapsucker holes from our idea of what Yellow Poplar bark looks like, then, we find these differences between it and Sweetgum bark:

• It's more brown that gray
• The ridges between the fissures aren't flat-topped

TREE BARK
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