Tree Finder - A Quick and Easy Way to Identify 50 Common North American Trees
Keys can use leaves, twigs, flowering parts and other tree characteristics to narrow down an unknown tree to a final classification. Some keys use terms that are a bit technical and a glossary is usually included to define terms mentioned in the key.
I have created a handy FAQ on how to identify trees. Start here and take my Tree Identification eCourse:
Tree Identification and Dendrology - FAQs
Beginning Tree Identification eCourse