Identifying Trees in the Winter from Bark
From the Tree & Landscape Board
When beginning tree identification, often much emphasis is placed on the leaf. A River Birch has serrated triangular (deltoid) leaves, a Dogwood tree has an elongated oval shape, and the towering White Oak has shiny, lobed leaves. But winter allows the budding dendrologist an opportunity to hone their identification skills by casting their eyes to the bark of the tree.
The bark that we can see is the outer bark, which is actually dead tree tissue. The tree’s vascular system is working tirelessly within the trunk, and the bark that we see on trees is the result of the inner layers of the tree growing and pushing outward over time to grow larger. A tree’s bark provides protection from heat, cold, insects, and pathogens, as well as regulating moisture for the rest of the tree to prevent it from drying out or rotting. Every tree species' bark has adapted differently to survive, and no two barks are the same.
Here are three common native trees in the area and what to look for when identifying them. The barks are quite distinctive and once you learn them it is easy to identify these trees!
River Birch (Betula nigra)
The River Birch (Betula nigra) is a fast growing medium sized (40’-70’ tall) tree with smooth, thin bark. In order to keep up with the blink-and-you’ll-miss-it growth of the birch tree, the bark has adapted an ingenious strategy; to shed its bark to allow for the rapid new growth, like a snake shedding its skin, or humans losing skin cells. The thin bark peels away as it quickly grows, overtime, creating a thick lower trunk with sturdy, protective bark. As the grey bark falls off, it will reveal the white-orange new growth beneath. The River Birch’s quick growth causes it to seed early in it’s growth which attracts songbirds, and the leaves are used to nourish beneficial butterflies or moths as they grow.
The Dogwood (Cornus florida)
The Dogwood (Cornus florida) is a small (20’-30’ tall), very slow growing tree, so the thick bark has time to grow strong with the tree, rather than a race to the finish like the River Birch. Dogwood tree bark is hard with a scale-like pattern and grey-brown in color. The pattern is similar to a reptile’s skin with small blocks. The bark allows it to adapt throughout the year providing various emphasis on weather insulation, protection from seasonal insect threats, and often allowing it to blend into its surroundings and go unnoticed by-passing herbivores. In the spring, its the Dogwood flowers attract pollinators, and its berries are an invaluable source of fat for wildlife.
White Oak (Quercus alba)
White Oak (Quercus alba), the Maryland State Tree, is a large tree (up to 150’ tall!) that grows slowly, with grey-white bark that has long ridges that will start to peel as it grows. The blocks of bark tend to be flat, or platy, as opposed to furrowed like on a Red or Chestnut Oak. Unlike the River Birch, which has thin, paper skin that it sheds throughout the year, the White Oak’s bark will only begin to peel once it’s older and more established. White Oaks are unparalleled in their ability to host various forms of wildlife in the tree’s 200–600 year lifetime, providing shelter, food, and increasing the air quality wherever it’s planted. They also tend to have widely spreading crowns when mature. One massive White Oak in Maryland, known as the Wye Oak, was approximately 460 years old when it collapsed in a thunderstorm June of 2002. Note to the budding dendrologist: oaks can be tricky to identify by bark, as many of them have the similar grey-brown, ridged appearance. Look at the ground below and around the tree for clues; old leaves, acorns, and its habitat can help narrow down which type of oak you’re looking at. One clue is the shade of the bark color on a White Oak which tends to be lighter, or more ash like in color, than of other oaks.
Identifying trees from bark is very useful because one does not always have leaves and buds to observe. Once you learn a tree’s bark look at many trees of the same species and see how variable the bark can be. With different soil types, hydrology, and other site conditions, one will start to decipher variations in a species bark. When one becomes accomplished at identifying a bark one can do it very quickly. Here are some other trees with distinctive bark; Pignut Hickory, Black Cherry, Black Locust, and how about White Pine. Learning the bark of a tree is an easy way to ID a tree. It's like learning a new language; the more that you use the skill the easier it is to do.
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