Invasive Phragmites management recommendations

Reversing and slowing the spread

Drone surveils phragmites

Reversing the spread of invasive Phragmites in Minnesota hinges upon implementation of proven management practices and effective partner coordination. University of Minnesota researchers, in partnership with MN Department of Natural Resources Aquatic Invasive Species Specialists, have resources to support control of invasive Phragmites populations. Local-level partner organizations, such as lake associations and county agricultural inspectors (CAIs), are leading control efforts in several different regions of the state. This team is working together with these groups toward comprehensive control of invasive Phragmites populations statewide. 

If you are pursuing control of invasive Phragmites, please contact Julia Bohnen or Chelsey Blanke with questions and to plug into the statewide control effort. 

We appreciate partners reporting their invasive Phragmites control work to avoid duplication of effort and to allow for statewide assessment of the status of this invasive grass.

Management recommendations summary

Multiple years of treatment will be needed to achieve effective control of invasive Phragmites. The following is an overview of a best practices management plan for invasive Phragmites control:
Summer mow (optional) —> Fall herbicide —> Winter mow (optional) —> Evaluate —> Follow-up treatment

This recommended sequence was developed following a thorough review of the Phragmites management literature and has successfully eliminated numerous populations since the statewide control effort began in 2020. Timely treatment with appropriate management techniques requires significant investment, but produces better outcomes and is more cost-effective in the long run compared to poorly timed and/or ineffective techniques.

Important points of caution

  • Confirm ID – Invasive Phragmites may be easily confused with native Phragmites. Be sure to confirm the identity of the stand as invasive so that native populations are not harmed. See the MNPhrag ID Guide for a comparison of distinguishing features.
  • Permits - Managing invasive Phragmites below the ordinary high water mark in state waters requires a permit—regardless of whether the management technique is mechanical or chemical. Contact your local DNR specialist or go to the Minnesota DNR's website for more information.
  • Prevent further spread - Clean all equipment and personal attire prior to leaving a Phragmites site to prevent transporting seeds or plant fragments that can cause new invasions. Right-of-way mowing during the growing season when stems are green is likely a significant source of spread via stem fragments.
  • Other treatment options - Mowing alone, burning alone, grazing alone, or covering with black plastic are not effective for long-term control of invasive Phragmites. In sites with standing water, cutting beneath the surface of the water may be used to drown the plants. Cut stem fragments must be contained and disposed of properly to prevent further spread.

Detailed management recommendations

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Detailed management recommendations

Summer mow (optional)

  • A summer mowing pre-treatment followed by a period of regrowth may be used before chemical treatment to increase the efficacy of the herbicide treatment by increasing herbicide contact with living tissue via the removal of dead standing stems.
  • If used, mowing should occur 6 - 8 weeks prior to the herbicide treatment to allow adequate regrowth.
  • Mowing pre-treatment may not be needed if the stand does not have significant dead standing mass.
  • Live stem fragments deposited in damp to wet locations can develop roots and shoots within 5 weeks, so mowing or cutting should not be undertaken if live stem fragments cannot be contained and managed in place. Sites of particular concern include 1) aquatic sites with standing or flowing water where fragments could drift away and 2) roadways, railroads, and etc., where the mowing equipment may move stem fragments along the right-of-way corridor.
  • Offsite disposal of cut material may not be feasible. Explore disposal options prior to mowing: 1) don’t mow, 2) leave cut material in place, 3) compost in an on-site upland location, or 4) transport to an approved disposal site.

Fall herbicide

  • Apply herbicides from August 1 to October 10 or until a hard frost occurs. Treatment after frost is not likely to be effective.
  • Use imazapyr (preferred) or glyphosate, alone or in combination.
  • Use an approved aquatic surfactant, i.e. those that are practically non-toxic or only slightly toxic to aquatic organisms. Vendors from this list sell approved aquatic surfactants.
  • Herbicide products formulated for use over water are required for treating Phragmites growing in standing water.
  • Application of imazapyr (Habitat) over water can only be made by certified aquatic pesticide applicators.
  • Treatment of large stands may require specialized herbicide application equipment (drone, Marsh Master) in order to achieve adequate application.
  • Follow all label requirements.

Winter mow (optional)

  • A patch may be mowed or physically knocked down if the patch has substantial dead standing stems prior to or after herbicide treatment. Mow or knock down in late fall or winter to manage dead standing stems to prepare the site for the next season’s herbicide treatment.
  • Allow 2-4 weeks for a fall herbicide treatment to take effect before winter mow/knockdown.
  • Mowing/knockdown should not take place until 1 or more treatments have been conducted and plants do not produce viable seed.
  • Do not mow/knockdown if seed heads appear fluffy and may contain viable seed. Equipment used for mowing/knockdown may pick up seed and disperse it to other sites.
  • Burning may be used in lieu of mowing/knockdown.
  • Winter mowing/knockdown may be preferable to summer mowing in areas where access is limited due to wet conditions and on aquatic sites with a risk of dispersal of stem fragments.
  • See disposal information under Summer Mow

Follow-up treatment

  • Monitor annually in late summer for up to 5 years post treatment.
  • Repeat the fall herbicide treatment until no regrowth is found during monitoring.
  • Follow-up fall treatments beyond 3 years may be necessary to achieve control.


  • Active revegetation may be necessary if, after the full cycle of treatments, native vegetation does not re-establish from the seed bank or from surrounding established vegetation.
  • Do not start revegetation efforts until monitoring has demonstrated that invasive Phragmites has been adequately controlled.
  • Revegetation will be most effective after dead standing stems are removed or thatch from mowing is largely depleted. For long-established Phragmites patches it may be necessary to physically remove the thatch layer or burn it off.
  • Revegetation should not occur until imazapyr residues have degraded from the soil.
  • When additional herbicide treatments may be necessary, an inexpensive cover crop could be considered for sensitive sites where soils are exposed.
Further Reading:

Note that while the number of invasive Phragmites populations in Minnesota has increased since development of the report listed above, and the control effort is currently more centralized than described, the report still provides useful context for understanding the status and threats of invasive Phragmites in Minnesota. You can also view our May 2019 webinar summarizing the assessment and read responses to questions that were asked during the webinar.