Dendrology – Learn to Identify Forest Trees
a Penn State Forest Stewards series article – written by Jim Finley, Professor Emeritus, Forest Resources Management, Center for Private Forests at Penn State.
Over the past year or so have you discovered a new or stronger connection to forests and trees? Those who study outdoor recreation have documented nearly explosive growth in the number of people exploring and spending time in parks and forests. Whether you are an old hand, used to spending time in sylvan landscapes, or a new convert to outside activities, have you found yourself looking in new ways at forests and wondering: What type of tree is that?

Forests are complex communities that depend on the interaction of the living (e.g., plants, animals, insects, fungi in soils) and non-living (e.g., soil structure, water, nutrients, weather, climate) components. Learning to identify, classify, and understand the role of each component’s contribution to forest function, health, and vitality describes the science of ecology, which seeks to understand and interpret these interactions.
To Understand Forests, Learn Your Trees
The first step in understanding forests is to learn to identify common forest trees. Right now (mid-summer) is a great time to learn the trees in your local area, as we are at the peak of the annual growing season – leaves are mostly full size, and it is the easiest time in a tree’s seasonal life to identify individual species.
Once you identify a species, say a red maple, which is the most common tree in the state, look around and recognize other individuals of that same species using the leaves as the principal characteristic for that species. Notice how individuals vary; obviously, they will differ in height and diameter. The bark on red maples of different size might look different. For red maple, the bark on smaller trees is smooth and silvery grey. As the diameter increases, small circular patterns with tiny potato chip-like raised bark flakes develop. On larger trees, this bark pattern will remain in place along with similar vertical flakes throughout.
Key Clues to Indentifying Tree Species
One of the tricks to the identification of any tree species is to recognize leaf types and arrangement. For instance, white pine is the only tree which has needles in bundles of five.
The second trick is to remember where you see the tree and then to visit it during the different seasons. When does it flower, show first leaves, drop leaves in autumn, and how do those events vary across the forest?
Identifying Trees: Books, Keys, & Apps
Dendrology “picture books” provide images of leaves, buds, and bark. Widely available and often region-specific, these allow you to match a given tree’s characteristics to the image. These are useful in the field, where online resources and apps won’t operate.
(CFC Editor’s note: Another excellent resource is the Penn State Extension “Summer Key for Pennsylvania Trees,” a sort of science adventure method of dialing in on the species you’re studying by using visual clues. The PDF is free, and can be sent to you phone, kindle, or tablet for offline field use. )