Know Your Trees and Where They Grow

Forests are complex communities that depend on the interaction of the living (for example, plants, animals, insects, fungi in soils) and non-living (for example, 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. Even if you were to choose to study only a small part of forest ecology, it could easily encompass a lifetime of work.

Trees are the dominant plants that define or describe forests. Therefore, the study of trees and woody shrubs, or dendrology, is an obvious starting point for learning about and understanding forests. In fact, one of the first forestry courses budding foresters take in college is dendrology, where they learn to identify trees and shrubs. After a semester of dendrology, they move on to silvics, which involves studying the life history and characteristics of forest trees with a focus on how the environment influences their occurrence and growth.

The first step in understanding forests is to learn to identify common forest trees. Right now 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.

One of the tricks to the identification of any tree species is to recognize leaf types and arrangement. 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?

There are rich and varied resources for starting to study dendrology. Common tools include “picture books” that provide images of leaves, buds, and bark. Use them to match a given tree’s characteristics to the image. Nearly any bookstore or library will have shelves of these references often tied to the region or state where you live. Know that there are also many e-resources online. A quick search will yield a plethora of resources using pictures and keys to compare leaves, buds, and bark. While web searches are useful, they are not as “mobile” as printed resources.

Of course, there are also many phone-based apps. In fact, a search for tree identification apps for Android and iOS yields nearly overwhelming results. 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 there are apps for minor plants, flowers, insects, fungi – the list goes on. Some of these apps use images you take to compare leaves, buds, or bark to file photos. They are great fun and addictive in many cases.

Knowing your trees is the first step to answering other questions such as: Does it or would it grow where I live? Why is it growing here? Does it provide wildlife food? What conditions (for example, soils, moisture, elevation, light) best support its growth and development? 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 is 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 (for example, wind or logging) on very productive soils created the right conditions for it to capture the site.

Again, there are resources that will enlarge your understanding of silvics, which is fundamental to expanding and understanding forest ecology. There are two very useful, extensive books produced by the USDA Forest Service titled Silvics of North American Trees, Conifers – Volume 1 and Silvics of North American Trees, Hardwoods – Volume 2. Again, you can easily find these as downloadable documents or click the titles of the books to follow a link directly to them. 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. Many questions relating to a given species’ requirements, at least important basics, are readily introduced in these references.

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

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 PrivateForests@psu.edu, or write to Forest Stewardship Program, The Center for Private Forests at Penn State, 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.

Written by Jim Finley, Professor Emeritus, Forest Resources Management, Center for Private Forests at Penn State