The Forestry Corner

By Ed Mignery, WY Tree Farm Committee

and Jeremy Dedic, WY State Forestry Division

Have you ever taken something for granted, then really looked at it and realized how special it is?

I have passed oak trees in our area many times. I did not give them much though or even a second glance. They are just bur oak. What a minimizing statement, “just bur oak”.

The current state champion bur oak tree is located by Sand Creek near Beulah. This tree’s trunk is over 40 inches across. The branches reach an impressive height and width. It is a beautiful yard tree where it resides. It is likely over 400 years old.

Driving up Lytle Creek road there are many oak trees among the pastures. They are short, standing about 30 feet tall. The trunks may be 10 inches in diameter. But they are also bur oak. I aged one unassuming tree. It turned out to be over 200 years old.

How is that majestic tree found off of Sand Creek, related to the bur oak growing in a pasture off of Lytle Creek?

Trees have variation in how they grow based on the environment of where they are. An area with warmer temperatures, plenty of moisture, with shelter from strong winds and deep snow, may have larger trees. These are environmental traits. Characteristics based on the environment.

But if you start looking at our bur oak and consider their characteristics, you will see more variations than just the form of the tree. Oak trees growing next to each other can have leaves of varying shapes, acorns of different size, shapes and acorn caps that are different. Even the bark of the trees can be different. Within a group of oaks either at Sand Creek or Lytle Creek we can find these variations. These are genetic traits.

These interesting genetics remind me of an old family, where there may be a suspension of heritage from long ago. Our bur oaks in the Crook County area are no different. They show many signs of possible hybridizing with gambel oak. Currently, the gambel oak‘s range is in Colorado and New Mexico. We are on the western edge of the bur oak range.

So let us compare these two similar trees and dig into this curious past. Referencing pictures of both of these oaks will help to compare their traits with the oaks from our area.

Bur oak has the Latin name Quercus macrocarpa. This means big nut. Bur oak has one of the largest acorn of the native oaks. They can be as big as a ping pong ball with a fuzzy cap covering over half the acorn. Gambel oak (Quercus gambelii) has small to medium acorns, as small as the tip of your little finger to the size of the end of your thumb. The cap of the acorn covers one third of the nut. We see both types of acorns on our oaks.

The leaves of both have variability in the shape, size and color. In general, both taper from a narrow bottom, by the leaf’s steam, to be very broad two thirds up to the top. The colors of the leaf can be a light green to a very deep dark green. There are even some trees that have a lighter margin on the leaf edge making a unique appearance of the leaves. Bur oak leaves can have very deep lobes, reaching almost to the center. Gambel have shallow lobes. These traits will vary from tree to tree.

Both trees reproduce from acorns and root sprouts. Either variety of tree will respond to damage (such as wildfire or equipment damage) by producing sprouts from its roots.

When these trees root sprout, it is prolific, causing thick regrowth. The resulting form is shorter and tends to be bent. The gambel is more prolific at this trait than the bur. It can develop very thick stands of short trees.

A frequently observed trait, thick stands of oak can hinder growth of grass and forage. There are areas with oak replacing the longstanding pines. Control of oak is difficult and expensive. Cutting of the stems and directly treating the stump with the proper herbicide can reduce sprouting.

Spraying re-sprouts the following year of has been promising. On the flip side, there are other landowners who utilize the acorn production and new stem growth as part of their wildlife habitat improvement program. Both are a major food source for deer, turkey and other wildlife.

The heritage of our oaks is interesting to speculate about as it dates back to the last ice age. Did bur oak in northeastern Wyoming cross pollinate with trees that now reside hundreds of miles to the south? How will the traits from these two species affect the characteristics of our forests in the future? While they are just bur oak in the eyes of some, perhaps we should consider how these oaks can be advantageous to range management and ecologic health? Can we manage oaks as a resource that benefits everything from grazing to water quality and habitat?

Whether they are bur oak or a hybrid with gambel, they have found our corner of the state to their liking. We find our area in the crossroads of native tree diversity. Bur oak are mainly a midwestern tree, with the Black Hills being on the western extremity of the range. They are found in their natural habitat, nowhere else in Wyoming.

Join us again at “The Forestry Corner” in a month or so and learn more about our interesting forests and trees.