What acorns have to say

You’ve probably seen a red oak before… and a bur oak and a white oak, though those two are tough to tell apart. That’s just three of the six hundred species of oak trees that exist world wide. In North America alone there are about ninety different species, sixty nine of which are native. These trees are everywhere and are particularly dominant components of forests in the Southwestern and Southeastern United States.

All of these trees are in the genus Quercus and all of these trees have acorns. In fact, the physical characteristics of a tree’s acorns can be really helpful when trying to identify what species of oak the tree is. For example, Northern Red Oak, orQuercus rubra, has acorns that are about one inch in length and they tend to have a shallow, scaly cup. On the other hand, the burr oak, aka Quercus macrocarpa, has larger, two inch acorns with deep, fringed caps. The difference between the two is striking.

Now, it would take a lot of time to explain how to identify each and every one of the sixty nine different North American oak species. That’s what field guides are for. But to get you started right here, right now, let’s look at a more general classification than species. The North American native oak species can be divided up into three groups, the red oaks, the white oaks, and the golden cup oaks. The golden cups are best identified by the golden cups on their acorns. The other two groups have a few more defining characteristics.

The species within the red oak group usually have bristle tipped leaves with pointy lobes. Their acorn shells are hairy on the inside and the cups are covered in flat, usually brown scales. If it’s winter and all you have to go by are buds and twigs, trees that fall into the red oak group usually have buds that are larger and pointier than those in the white oak group. The bark of the red oaks is usually dark in color with smooth ridges and no peeling.

The species that fall into the white oak group have rounded lobes and no bristles. Their acorn shells are not hairy on the inside and the cups are generally paler with knobbier scales. Twigs have blunter buds and bark is paler and scalier, sometimes to the point of peeling.

So try that on for size. Next time you’re out and about, look at the trees around you and try to first determine whether or not they’re oaks, and then which oak group they would fall into.

Happy tree id-ing.

Source

Sibley, David. The Sibley Guide to Trees. New York: Alfred A. Knopf, 2009. Print.