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Issue No. 3, Article 7/April 8, 2005

What Weed Is That?

Weed identification is the first step in weed management, introducing the need to have various reference materials at your disposal. We have categorized several identification resources into groups based on the emergence timing and maturity of the plant species they include. All but one of the publications in this article can be found under the Weed Identification section of the North Central Weed Science Society Extension Publications page (please click on the Extension Publications button). From this Web site, you can view, print, and/or order these publications.

Early-Season Weeds

Two publications that are extremely useful for identification of early-season weeds include the Early Spring Weeds of No-till Crop Production and A Pocket Guide of Early Season Weed Species. The first publication, Early Spring Weeds of No-till Crop Production, is in full color and 22 pages long. It contains a taxonomic key along with many photos of 45 weeds and text descriptions. Also included is a guide to herbicides for control of the weeds included in the publication. A Pocket Guide of Early Season Weed Species is a pocket-sized reference to 19 early-season weeds with color photos and descriptive text. Also of note is a one-page identification sheet for several winter annual grasses.

The Weed Seedlings of Summer

Only a few publications focus on summer annual weed seedlings. We are going to highlight two of our favorites. Weeds of the Northeast has 299 weeds, with color images of these weeds from seedling to mature. There are also many keys and helpful tables for distinguishing closely related plants. Common Weed Seedlings of the North Central States is a 21-page bulletin with color images of 36 broadleaves, 17 grasses, and 1 sedge along with text descriptions.

Mature and Flowering Weeds

Most of the weed identification resources fall into this category, albeit contrary to the idea that you need to identify weeds when they are small in order to control them. Nonetheless, here are some of the better mature-weed identification publications. Weeds of the Great Plains, spanning over 600 pages, has been recently revised and now contains color images and text descriptions for 266 weeds. Another good book to have around is Weeds of the North Central States, which contains 230 species with black and white line drawings of mature plants and key characteristics.

For the technologically savvy, the Interactive Encyclopedia of North American Weeds DVD offers more than 2,400 photographs covering 447 of the most important weeds and crops in the United States and Canada. This DVD also contains an illustrated interactive identification key and a comprehensive glossary of plant identification terminology.

Finally, we are frequently asked to identify plants that are not usually "classified" as weeds, so we tend to use wildflower identification guides. Wildflowers (Peterson Field Guide) and Newcomb's Wildflower Guide are great references for plants not typically found in cultivated areas. These books can be found at libraries, bookstores, and online book suppliers.--Dawn Nordby and Aaron Hager

Aaron Hager
Dawn Refsell

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