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?

PAFS - Dendrology - identify forest trees

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. )

Of course, there are also many phone-based apps – and, very likely, once you look and try some of these resources, they will capture your “budding” interest in dendrology. They may even take you further to other tools useful in knowing your forest, as apps exist for identifying plants, flowers, insects, fungi – and some, like imapinvasives, allow everyone to help scientists track populations of invasive species for research or treatment. 

Knowing Your Trees Unlocks the Landscape

Knowing your trees is the first step to answering other questions such as: 
  • Why is it growing here? 
  • Does it or would it grow where I live?
  • Does it provide wildlife food? 
  • What conditions (e.g., soil types, moisture, elevation, light) best support its growth and development? 
  • Is it facing threats from invasive species (e.g. HWA – hemlock woolly adelgid), forest pests, or disease?
As you spend more time afield working at dendrology, you will notice that some tree species appear or occur on specific sites, and you will, in time, develop some basic ecological skills for predicting where you will find them.  Red maple is a “generalist” as it is can thrive across a given landscape or forest; that is one reason why it’s the most common tree in the state. On the other hand, tulip poplar, while common in some parts of Pennsylvania, requires certain conditions for seed germination and adequate light, moisture, and nutrients to thrive. As a result, it is often found in groupings where a past disturbance (e.g., wind or logging) on very productive soils created the right conditions for it to capture the site.

Silvics - Trees in their Environment

Silvics, the study of the life history and characteristics of forest trees with a focus on how the environment influences their occurrence and growth, is fundamental to expanding and understanding forest ecology. There are two very useful, extensive books produced by the USDA Forest Service titled:

The amount of research-based information underpinning these two references is amazing and approachable. For each tree species, there is a distribution map showing its natural range, which is fascinating (well, at least to some users). The introduction to each book is a silvics primer, which shares how trees respond to environmental conditions and even provides insights into their response to human-caused climate change.

For each species, there are sections on their habitat needs, including: 

  • Distribution Range (climate tolerance, soils, and topography, associated forest cover);
  • Life History (reproduction and early growth, flowering, seed production, seedling development, vegetative reproduction (e.g., stump sprouting));
  • Sapling to Maturity (rooting habit, reaction to competition, damaging agents);
  • Special Uses; and
  • Genetics.

Education Inspires Conservation

Increasingly, as our climate changes and as we find solace and comfort in forests, there is clear value in learning more about the woods, and their trees. Appreciation of forests will expand as individual understanding increases, and familiarity is likely to further conservation. 

The next time you visit your favorite park, woodlot, or forest, take a few minutes to identify a new tree and make it your friend.  Our forests need your support.


emphasis and headings supplied by Cook Forest Conservancy, and apologies to the author!  

The Pennsylvania Forest Stewardship Program provides publications on a variety of topics related to woodland management. For a list of free publications, call 800 235 9473 (toll free), send an email to, or write to Forest Stewardship Program, The Pennsylvania State University, 416 Forest Resources Building, University Park, PA 16802. The Pennsylvania DCNR Bureau of Forestry, USDA Forest Service, Penn State Extension, and the Center for Private Forests at Penn State, in Partnership through Penn State’s Department of Ecosystem Science and Management, sponsor the Forest Stewardship Program in Pennsylvania.