By Emilie Justen
Minnesota Department of Agriculture 

March Weed of the Month: Change to the 2021 Noxious Weed List

 

Non-native phragmites growing on the edge of a pond in Wright County.

The Minnesota Department of Agriculture (MDA) has made one change to the state's 2021 Noxious Weed List. The designation of the non-native subspecies of phragmites (Phragmites australis spp. australis) has changed from Restricted to Prohibited Control. Though the list typically changes once every three years, the MDA is making this change due to a delay resulting from the Noxious Weed Advisory Committee (NWAC) 2019 recommendation to change the status.

The regulations do not apply to Minnesota's native subspecies of phragmites (Phragmites australis spp. americanus). The Minnesota Aquatic Invasive Species Research Center (MAISRC) has information on distinguishing between the two subspecies. You may also work with your local county agricultural inspector for help in determining which subspecies you may have observed. County agricultural inspectors are great resources for plant identification at the local level and can be connected with biologists at the University of Minnesota, the MDA, and other state agencies for help with identification.


As the lead agency for noxious weed regulation, the MDA, with recommendations from NWAC, updates the state's Noxious Weed List. The Noxious Weed List places weeds into four categories, Prohibited Eradicate, Prohibited Control, Restricted, and Specially Regulated Plants, and defines how the weeds must be controlled. Plants are placed on the Noxious Weed List because they may be harmful to public health, the environment, public roads, crops, livestock, or other property. To view the updated Noxious Weed List and to learn more about the category definitions, go to the MDA website.

Prohibited Control weeds are more widespread than Prohibited Eradicate weeds. Prohibited Control weeds must be eliminated before they mature and spread through seeds, cuttings, and other plant parts. Efforts must be made to prevent seed maturation and dispersal of plants into new areas. Additionally, no transportation, propagation, or sale of these plants is allowed.

Non-native phragmites is a semi-aquatic perennial grass that grows in wetlands, lakeshores, streambanks, and marshy areas. It can reach heights of 15 feet and forms dense clonal stands. The stems are hollow, ridged, and rough in texture. Flowers develop in August and form dense, feathery clusters that are typically purple in color. Roots and rhizomes (underground stems) can spread more than 10 feet horizontally and several feet deep. It also produces a high number of seeds. With its extensive underground system and seed production, it outcompetes native plant species and degrades wetlands by reducing the movement of sediment.


Management of non-native phragmites can be challenging. A combination of mowing, herbicide treatments, and following up with additional herbicide treatments and controlled burns have been successful. The University of Minnesota (U of M) has conducted research on management tactics and has recommendations available to the public. Make sure to check state pesticide laws if applying herbicide near water. To treat phragmites submerged in water, obtain a permit from the Minnesota Department of Natural Resources.

The MDA, Department of Natural Resources, Minnesota Pollution Control Agency, and researchers at the U of M are working with wastewater treatment facilities in the state that use non-native phragmites in their remediation ponds. Wastewater treatment facilities adhering to state approved best management practices for preventing spread will be exempt from the Noxious Weed Law until research identifies suitable alternative plant species, with the ultimate goal of enacting a phase-out of the use of non-native phragmites in wastewater treatment facilities.

 

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