Glyceria maxima

2017 identification and mapping project

Glyceria maxima (reed manna grass) is a perennial rhizomatous grass.  It is known to invade wetlands, including swamps, ditches, wet pastures, and lakes, ponds, slow-moving rivers and creeks where it forms low diversity stands that are capable of crowding out native vegetation and animals.

The species is currently split-classified under NR40, Wisconsin’s invasive species law. It is restricted (orange) in southeastern Wisconsin, and prohibited elsewhere (red). In the Midwest, the plant’s distribution is confined to Wisconsin, Illinois and perhaps Minnesota. Since it has limited distribution in Wisconsin, we hope to both reduce its spread to the western part of the state and eliminate stands where possible. Most populations are located in southeastern Wisconsin, between Milwaukee and Madison, with others in Calumet, Outagamie and Oneida Counties.

During the 2017 field season, SEWISC is working to identify, map and record over 200 reported G. maxima populations on public and private lands in our region. This survey information is shared with our project partner, the Wisconsin DNR, who will work with landowners to manage the populations. An experiment to control this species is currently underway in Dane county and initial observations look promising for complete control.

The Glyceria genus is typically distinguished by having closed leaf sheaths, angular shiny blades, and broad, stiff branched seed head (panicle). Click HERE to learn more about reed mana grass ecology and identification.

If you suspect this species to be on your property or if you see it elsewhere, please contact:

Jason Granberg