We frequently receive questions about how to identify weeds and what the best resources are to help with identification. There are many resources available for plant identification, but these are some of the ones we use the most, divided into four categories – books, online pdf’s, websites, and apps (internet access not necessarily required except to download initially). We still often start the identification process with several books, because this can be faster and more comprehensive than using the web.
We have shelves of ID books and all of them serve a purpose. They are full of amazing descriptions, sketches, and pictures. Our top picks, in order of preference are: Weeds Of the Northeast, Weeds of the Midwestern United States and Central Canada, and Weeds of the North Central States. These are all available for purchase on the web.
2. Online pdf’s
Weed seedling ID - http://fieldcrop.msu.edu/uploads/documents/Ncr607.pdf
Early spring no-till weed IDhttp://weeds.cropsci.illinois.edu/extension/Other/NCR614.pdf
Many solid weed ID websites are available, and the best one is really a matter of personal preference. Weed science programs at Virginia Tech and the Universities of Illinois and Wisconsin have good ID sites. A favorite for just looking at photos of weeds is http://images.bugwood.org. The “images” tool in Google is very helpful for confirming an ID.
- good arrangement and labeling
- written descriptions better than some pics
- database with search options
“ID Weeds” from University of Missouri Extension. A little technical; however, a solid weed list with a good vocabulary to get you headed in the right direction.
Weed ID” by BASF. This one has a “take a picture” option that can be very helpful. It also has general ID pictures instead of just terms when choosing characteristics.
Ag Weed ID by Penton Media Inc.. Has a Compare Image option that is nice, or browse option with unique narrowing search option
AG-PHD by FM - multiple tools, has a pest detection section with list of weeds and photos
Invasive Plants in Southern Forest: Identification Management - specialized list of species
Federal Noxious Weeds Key by USDA - seed and fruit for the hardcore ID
The first and normally easiest step in identification is determining if the weed is a monocot (grass) of dicot (broadleaf). If you go with grass the main characteristics to look at are the leaf shape, presence or absence of hair, auricle, ligule, flower shape, and overall plant structure. If you go with broadleaf the main characteristics are cotyledons (if still present), hair (present or absent), leaf arrangement, leaf type, leaf shape, leaf margin, petioles, ochrea, and flower shape/color. With all of these characteristics a lot of variation occurs, and not just between species but within as well. Feel free to email us for help with weed identification. We can often identify a weed with a few good digital photos.