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Cofrin Center for Biodiversity



Online Keys

If we are to learn to recognize the species of trees in their diverse forms we must learn to recognize reliable character differences between similar species, and to understand the range of variability within each species. The mechanism most often employed for learning these characters is a "dichotomous key" based on a set of diagnostic characteristics that have been confirmed by use over a wide area and a large number of individuals. A dichotomous key may be thought of as a word tool in which the user is presented with two exclusive alternatives (e.g. leaves opposite or alternate) and chooses the alternative that best fits the plant in question. That choice leads to another set of two alternatives from which the best choice is accepted, and so on, until the user reaches an answer. With practice, as the user learns to understand the terms, it becomes easier to quickly narrow the possibilities to a small subset of species, within which a few critical characters can be examined to conclude the identification. 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.

Gary Fewless has developed the following dichotomous keys to the trees and ferns of Wisconsin. These keys can be used to correctly identify

Trees of Wisconsin

The key includes all the trees known to occur in Wisconsin outside of cultivation (native, naturalized and escaping from cultivation). It does not include species known only from cultivation, except for a few gymnosperms clearly identified as such, and it does not intentionally include shrubs. However, species of intermediate form and those variable enough to be considered either tree or shrub under certain conditions have also been included. Based on these criteria, 118 angiosperms and 12 gymnosperms have been included for a total of 130 species (three additional species of gymnosperm shrubs are included in the key for convenience and they are repeated in the shrub section).

Ferns of Wisconsin

This site provides a key to all Wisconsin pteridophytes with photos and descriptions to help with their identification. If the key is successfully employed to identify an unknown plant, the reader is directed to a page providing photos of the species and some basic information regarding habitat and distribution. The reader can also go directly to a list of Wisconsin ferns and fern allies to get to the photo pages.

Online Lists

The following lists provide detailed descriptions of individual species. The lists are organized by Latin names as well as common names. Unlike the keys above, these lists provide species descriptions only.

Shrubs of Wisconsin

This list includes all of the species of shrubs found in Wisconsin. Perhaps 20-25 of species treated as trees in this key might also be considered shrubs. An additional 210 species (including the troublesome Rubus, Rosa and most of the Crataegus species) would be classed as shrubs, and another 25 species as woody vines for a total of about 365 woody species. A separate treatment of the shrubs of Wisconsin is under construction and a unified key for all woody species of Wisconsin is a long-term goal.

Wetland Plants of Wisconsin

This page is intended to provide images and descriptions for vascular wetland plants of Wisconsin. It includes approximately 200 species, including many common and important species and a few that are less common. This is by no means a complete list--the total number of wetland plants for Wisconsin is probably in excess of 700 species. The list will grow as time and the availability of images allow.

Goldenrods of Wisconsin

As currently understood, twenty four species of goldenrods have been reported to occur in Wisconsin. Some authors would raise the number of species to 25 by distinguishing Solidago altissima as a species separate from S. canadensis. Others have placed S. ptarmicoides in the genus Aster, reducing the number to 23. Perhaps 6-10 species could be considered common, at least in some significant portion of the state, and other species may be locally common in a particular area. One species, Solidago canadensis, is so common, widespread and variable as to be emblematic of the genus.

Asters of Wisconsin

There are a total of 30 Asters known for Wisconsin, 29 in the genus Aster plus Brachyactis ciliata (Ledeb.) Ledeb., once known as Aster brachyactis. Leaves, including basal leaves are often important key characters, as are the phyllaries. As always, it is important to record the live color of the ray flowers and carefully considered habitat descriptions can be very helpful.

Invasive Plants of Wisconsin

The following plants are the most serious invasive species in northeastern Wisconsin. This site is designed to provide images to help in identifying these plants. There are numerous sites on the web with good information on these species, including control methods. If you find a population of one of the invasive species in Wisconsin you may report it to the Wisconsin invasive plants reporting and prevention project.

For more information and links concerning invasive plants in Wisconsin contact the

Wild Rice Database (temporarily offline)

Wild rice is the common name for plants in the genus Zizania. Worldwide, there are 4 species, two of which are native to Wisconsin: Z. aquatica and Z. palustris. Wild rice has historically been widespread throughout much of Wisconsin. Over time, many rice beds were destroyed as wetlands were drained or waterways were modified, and landowners cleared shorelines for docks and beaches. The database contains downloadable GIS layers that show the locations of historical and extant populations of Zizania in Wisconsin. Email if you would like access to a zipped file of the database.