If you are new to grass ID, or even experienced with it, and you come across an unknown grass, the options of possible grasses can be overwhelming! In Illinois, there over 400 possibilities, including subspecies and varieties. Luckily there are several online mapping tools that are easy to use that can help you narrow down the possible options that the grass could be. We’ll look at those tools in today’s blog and work through an example together.
The tools
USDA Plants Database
The USDA Plants Database is an online tool that houses a wealth of information about the plants found in the U.S. I use it most often to look at distribution maps, which are available for each species. The distribution data comes from publications and herbarium databases, with the original data coming from BONAP (listed below). Depending on data availability, it will show where the species is found at the state or county level. It also reports if plants are native or introduced.
You can also download a report by county of all the species in a given family, like the grasses, or for any other search criteria.
North American Plant Atlas
Another resource that is helpful is Biota of North America Program's (BONAP) North American Plant Atlas. This includes county level data for the plants found in North America north of Mexico. I find this resource most helpful when I am sure a plant is in a certain genus, and I want to see what different species options there are for my county. For example, I find a grass that looks like a foxtail but I want to know what different species are found in my area to help narrow down my options, I could go to the Setaria page and see all the different species found in my county. Then I can use whatever my preferred field guide or online resource is to look up the different species and read about their characteristics to help make my ID.
EDDMapS
Finally, a resource that is great for tracking invasive species, many of which are currently spreading into new locations, is EDDMapS. EDDMapS is a widely used online platform that documents and shares information on invasive species, pests, and biocontrol agents across the U.S. Anyone can add observations to the map, so this is a leading resource for finding new reports of infestations in counties where they may not have been historically located. Learn more about EDDMapS over on the Everyday Environment blog.
Working through an example
Let's say I came across a grass I didn't know when I was out hiking in Johnson County. The grass has auricles; weak, thin shiny green leaves; and a spike inflorescence with awns.
Let’s go to USDA Plants and do a state search. Here I would input Poaceae for family, Illinois for state, and Johnson for county. The results would show me 155 species (including subspecies and varieties). Not nearly as many as the 400 in Illinois, but still a lot! Another helpful feature is that you can narrow your search by annual or perennial. Many annual grasses pull easily out of the ground, so giving the grass you find a gentle tug can help you narrow down your search even more.
Next I would look at the characteristics of grasses at the genus level, to see if the characteristics of that genus match my grass. In this example, there are 49 different genera of grasses in Johnson county. I would use a field guide and thumb through the pages to find grasses that have characteristics that match whatever grass I am trying to identify. Looking back at the characteristics listed above, they would lead me to look at the Elymus genus, or the ryes.
Then I could reference the state search to see there are only 5 species in that genus in Johnson County: Elymus canadensis, Elymus hystrix, Elymus repens, Elymus villosus, Elymus virginicus. Now I only have five grasses to compare with a field guide or other online identification resource - that's not bad at all!
On the other hand, if I found a grass in a field guide that matches the grass I am trying to identify, I could look up that grass on one of these online tools and see if it has been reported in the county I found it.
Have you used these range map tools before? Which one is your favorite?
Thank you for reading! Need a refresher on grass identification terms, like ligule and spikelet? Check out this blog post!
About Grasses at a Glance
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ABOUT THE AUTHOR: Erin Garrett is a Natural Resources, Environment, and Energy Educator for University of Illinois Extension serving Alexander, Johnson, Massac, Pulaski, and Union counties. Erin develops and delivers high impact programming to adults and youth to help them develop an appreciation for natural resources and to empower them to make small changes to positively impact the environment. Erin’s programming focuses on why homeowners should consider choosing native plants, how to support native pollinators, how to identify grasses, how to identify and manage invasive species, and developing an appreciation for prairie ecosystems.