This site is intended as a resource for those interested in the 130 species of trees growing outside of cultivation in Wisconsin. See the text at the beginning of the key below for an explanation of the number. Cultivated species are not covered in this web site, unless they also escape and reproduce on their own. A page is provided for each Wisconsin tree species with photos and descriptions. A key and a glossary are provided to help with their identification and an introduction to tree and shrub identification is also provided for beginners.

It may be entertaining to compare unknown plants to pictures of known species, but it is a very risky business to identify them in that manner. If you are serious about learning the identity of plants (i.e. if it is important that the answer you arrive at is correct), you must learn to use one of the many keys available for that purpose. Photos can provide insight into the various terms used in the keys, but individual leaves, tree shapes, bark patterns, etc are so variable that no picture can adequately represent any particular species. Consider this example of extreme variation in three leaves from the same branch of a White Mulberry tree, or this selection of leaves taken from a single branch of a Thornapple, or a branch of a Choke Cherry.

One of the difficulties in learning to identify trees rests in the common desire among beginners for a single character that will distinguish a particular species. Because of the highly variable nature of plants, it is frequently necessary to consider several characters to make a reliable identification. That is why keys are essential. They can describe combinations of characters and a range of possibilities more accurately than is possible in a picture.