Tree Graphic Keys

In the “Key That Tree” activity you encountered a dichotomous key. By knowing how to use a “dichotomous key” to identify plants you will have mastered one of the most important skills of a forester or naturalist. The dichotomous key is a tool that will help you identify virtually any plant you encounter in the field.

“Dichotomous” refers to something “divided into two parts”. A dichotomous key is just a set of questions such that each question has 2 possible answers but only a single correct answer. It’s like following a path and you go through a series of places where the path splits into two. At each split you have to decide which path to take based on what you see in the tree specimen you are trying to identify.

To use a dichotomous key, however, you must be familiar with all the parts of a tree and the minute structural differences among those parts. Most field guides you can buy in stores are dichotomous keys. Get a field guide and start practicing your keying skills.

“Where can I get a key?” you may ask. Contact your local Extension Service and ask if your state has a tree identification publication. Otherwise, look in your local bookstore. Here are a few common references:

C. Frank Brockman. A Guide to Field Identification: Trees of North America. 1986.Golden Press, New York. 280 pp.

Ann H. Whitman, Ed. Familiar Trees of North America, The Audubon Society Pocket Guides. 1986. Published by Alfred A. Knopf, Inc.

There are many such guides. Try a web search on “Tree Field Guides” to find others.

Web Links:

Virginia Tech University’s Dendrology Website

An Interactive Key of Common Iowa Trees

Trees of the Pacific Northwest