Flowering rush confirmed in Grants Lake in Douglas County

First time invasive aquatic plant has been confirmed in county

The Minnesota Department of Natural Resources has confirmed small patches of flowering rush, an invasive aquatic plant, in Grants Lake in Douglas County. 

The DNR has begun removing the plants by hand. Hand removal can be successful in small populations like this one.  DNR staff will monitor the site for any regrowth and take appropriate further control measures if required.

Flowering rush is a weed-like plant with pink flowers that can overtake habitat, crowd out native species and make it difficult for boats to access open water. It is a perennial that grows one to four feet high along shores in shallow, slow-moving water.

In deeper water, it can grow in a submerged form that does not produce flowers. It flowers in early summer through mid-fall. Flowering rush can be difficult to identify when not in flower, as it closely resembles many beneficial native shoreland plants such as the common bulrush.

People can spread flowering rush primarily by moving water-related equipment and illegally releasing water garden plants into public waters. It reproduces by vegetative spread of small onion-like buds called bulbils, which can be hidden in mud and debris and can stick to boots, waders and other fishing and hunting gear.

Flowering rush is a prohibited invasive species in Minnesota, which means it is unlawful (a misdemeanor) to possess, import, purchase, transport or introduce this species except under a permit for disposal, control, research or education.

Whether or not a lake is listed for any invasive species, Minnesota law requires boaters and anglers to:

  • Clean watercraft and trailers of aquatic plants and prohibited invasive species.
  • Drain all water by removing drain plugs and keeping them out during transport.
  • Dispose of unwanted bait in the trash.

Some invasive species are small and difficult to see at the access. To remove or kill them, take one or more of the following precautions before moving to another waterbody:

  • Spray with high-pressure water.
  • Rinse with very hot water (120 degrees for at least two minutes or 140 degrees for at least 10 seconds).
  • Dry for at least five days.

People should contact an area DNR aquatic invasive species specialist if they think they have found flowering rush or any other invasive species that has not already been confirmed in a lake.

More information is available at mndnr.gov/ais.