A website from UGA Cooperative Extension

by Carole MacMullan, Fulton County Master Gardener Extension Volunteer

This article is part of Garden Buzz, a series from Appen Media and the North Fulton Master Gardeners, where rotating columnists explore horticulture topics like herbs, insects, and wildlife conservation. Find all Garden Buzz articles here.

Image by Gabrielle LaTora, UGA Extension Fulton County

Walking in the woods is always a refreshing and invigorating experience and good for the soul. Now that it is winter, a great remedy for cabin fever is to bundle up and take a winter walk.  As you walk, note the forest trees as well as the ground below your feet. Most if not all of the trees have lost their leaves.  As a result, a whole new visual landscape opens to our eyes and the leaf litter below us can offer clues about the trees that inhabit the woodland terrain. 

If you are curious about the types and names of trees, you can also quickly identity one of the dominant northern Georgia forest trees, the beeches. They have a unique characteristic because their paper-thin, light beige leaves stay firmly attached to their branches during the entire winter. Continue your walk by picking up some of the leaves on the forest floor. Note there are many tree species, but I venture to guess, most of them are oaks. You will also see a variety of acorns, most of which have been partially or totally devoured. All oaks belong to the genus Quercus. Based on their leaf structure, the genus Quercus is divided into two major types, the white oaks and red oaks. How can they be differentiated? White oaks have leaves with round leaf lobes and red oaks have leaves with pointed leaf lobes. Please look at the pictures and I am sure you can quickly distinguish between these two types of oaks. Oaks are the most valuable landscape and forest trees in the eastern United States. For this reason, oaks are considered a Keystone Tree. They have earned this designation because their acorns produce life-sustaining nourishment for a variety of living things. If oaks were eliminated from the eastern US, the entire ecosystem would suffer.

Left photo – A view of a beech tree grove with their winter leaves, photo by Carole MacMullan; Right top photo – Georgia oak; Right bottom photo – Two types of oaks: on the left, a chestnut oak, a white oak, with its acorn; on the right, a pin oak, a red oak, with its acorn. Photos by Carole MacMullan

As I write this article when the outside temperatures are hovering around freezing, I have begun to reflect on how the animals find food and shelter during the winter months. In my front yard, I have three mature pin oaks that have reached 30 feet and are now producing acorns.  Amazingly, most oak trees need to reach the age of 10 and pin oaks the age of 20 before they are sexually mature and produce acorns, and the number of acorns a tree produces will vary from year to year. In the spring, oaks produce inconspicuous flowers. Like all flowers, they need to be pollinated to produce seeds. Oak trees are pollinated by wind because the flowers do not contain nectar.  After pollination, the flower is gradually transformed over the late spring and summer months into an acorn. Each acorn contains a seed that has the potential, if the conditions are right, to germinate and produce another oak tree. To ensure a future generation, the oak trees create an excessive number of acorns.  This bonus crop of acorns provides a forest feast! Squirrels devour them and instinctively they bury some of them for future consumption. This squirrel activity is a WIN-WIN situation! The oak trees win since some of the buried acorns germinate. Many other woodland organisms, such as deer, opossums, racoons, rodents, insects, and fungi also enjoy this abundance of life-sustaining nourishment, which keeps them alive in the fall and winter. Acorns are consumed by a total of 96 species of birds and mammals in the U.S.  In addition, oaks provide food for more than 897 species of butterfly or moth caterpillars in the United States.

What do kangaroos and Georgia oaks have in common?  Both of them are endemic, meaning they originated, thrived and found an environmental niche in one specific location on the planet Earth and exist nowhere else.  What a surprise to find that the Georgia oak, Quercus georgiana, is a type of red oak and is endemic. The common and scientific names for Georgia oaks were selected because this species of oak lives primarily in Georgia and a few isolated sites in Alabama and South Carolina! This oak species is a small species of oak and often takes on the form of a shrub.  Over time, it has adapted to the dry granite and sandstone outcroppings and thin layer of soil found on two, low altitude mountainous regions of Georgia, Stone Mountain and Pine Mountain. I was fortunate to have seen one of these rare and endangered oaks on a recent hike at FDR State Park near Warm Springs, Georgia. 

There are 70 species of oak trees in the U.S., and 28 oaks are native to Georgia. Today I will focus on two common oak species that you will encounter on most walks in local parks, forested areas dominated by hardwoods, as well as in your yard or the yards of your neighbors, friends, and family.  From my observations, the most commonly planted medium-size trees found in residential Atlanta landscapes are pin oaks, Quercus palustris.  Pin oak leaves have four to six lateral lobes and one terminal lobe with pointed ends. As a result, they are classified as red oaks. White oak leaves, on the other hand, have lobes with rounded ends and acorns that germinate within two weeks of reaching the ground. White oak acorns also have less of the bitter tasting chemical, tannin, making them a more desirable food source for deer and other wildlife. 

Another oak that is native and easily identifiable is the chestnut oak, Quercus montana. My first encounter with this oak was not with the tree or a leaf but with its large, brown acorn. Next to the acorns were a collection of scalloped edge leaves. The leaves were quickly identified as a white oak because they have rounded lobes. The small, scalloped edged leaves, unlike those of other Georgia white oaks, helped me to narrow my selection to chestnut oak. 

On your next forest walk, pick up some leaves and try to identify the surrounding trees.

Happy gardening!

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About the Author

This week’s “Garden Buzz” guest columnist is Carole MacMullan, a master gardener and a Milton resident.She taught biology for 35 years in the Pittsburgh area. In 2012 after moving to Milton, Carole completed the Master Gardener training program and joined the North Fulton Master Gardeners (NFMG) and the Milton Garden Club. Her hobbies are hiking, biking, gardening and reading.