Minnesota Aquatic Weed Control in Ponds and Lakes

Here are some examples of aquatic weeds and how to control them in any of Minnesota’s 11,842 lakes, 6,564 natural rivers and streams and over 10 million acres of wetlands.

Curlyleaf Pondweed

Curlyleaf pondweed also known as Curly cabbage or crisp pondweed is a plant native to Africa, Australia, and Eurasia and was introduced in the United States in the 1800’s. By the 1930’s it was well established in the midwest and is now in all but 2 of the lower 48 states. This weed has become a major obsticle for Minnesota’s aquatic weed control in ponds and lakes.

Curlyleaf pondweed is a submersed aquatic plant with oblong, wavy, blue-green leaves that attach to its stems in an alternate pattern. Leaves can be up to 3 inches long and a half inch wide. The leaves have a “tooth-like” appearance to their edges. Curlyleaf pondweed produces small flowers that are arranged on spikes that rise a few inches above the surface of the water. Curlyleaf can grow in a variety of different locales and sediment types. This plant can tolerate extreme conditions including low light and cold water temperatures and has even been found growing under 20 inches of snow covered ice.

Curlyleaf pondweed is usually introduced to new bodies of water through the transport of plant fragments on aquatic equipment like boats and trailers. Curlyleaf’s dense growth can reduce the opportunity for water recreational activities and can decrease values of properties on lakes with a heavy infestation of the weed. Use RestoreAccess Ultra to control the invasion of this aquatic weed.

Purple Loosestrife

Purple loosestrife was first introduced to the east coast of the United States in the 1800’s for ornamental and medicinal uses. By 1940, most of the Midwest was invaded by this plant and by 1985 it had found its way across the United States to the west coast first spreading along roads, canals, and drainage ditches. There are about 2,000 recorded purple loosestrife infestations in 77 of the 87 counties in Minnesota. And are now found in lakes, rivers, or wetlands.

Purple loosestrife is a perennial that stands erect on a square, woody stem. Each rootstock can have 1 to 50 stems reaching a height of 10 feet. Green leaves sit opposite on the stem and are lance-shaped with smooth edges. This plant puts up many flower spikes and each spike is covered with five to six, pink to purple petals with yellow centers. Annually this plant can produce up to 2 million seeds the size of a grain of sand with 60-70% viability.
It is estimated that over 1 million acres of U.S. wetlands are taken over by this invader each year. It adapts well to any kind of wetland quickly crowding out native species leading to the displacement of native wildlife. For control Purple Loosestrife in your Minnesota lake or pond, Lake Restoration recommends an Open Water Kit, which is also effective in killing cattails and water lilies.

Eurasian Watermilfoil

Eurasian watermilfoil is a submersed perennial with a long underwater stem that branches at the surface of the water. The plants leaves are whorled (opposite) on the stem at each node with four feather-like leaves per whorl. It produces small reddish flowers that emerge several inches above the water on a spike grown from the tip of the stem.

The invasive plant can grow in a wide variety of habitats and conditions: ponds, lakes, reservoirs, and slow flowing rivers and streams. It will grow in shallow or deep water and does well in waters that have had some sort of disturbance like intense plant management, overabundance of nutrients, or extensive motorboat use. Eurasian watermilfoil has difficulty becoming established in lakes with well established populations of native plants.

We recommend that you use treatments once plants are established but before flowering occurs. RestoreAccess Ultra is perfect for controlling this weed in Minnesota ponds and lakes. We do not recommend mechanical removal unless invasion is widespread as fragmentation of the plant can aid in its spread since dispersal through vegetative means is its main reproductive strategy. If that is the case we recommend using Lake Restoration’s LakeMaid.

MN DNR map of Eurasian watermilfoil infestation

Non-Native Waterlillies

The non-native water lily (Nymphaea spp.) is a perennial aquatic herbaceous plant. You will find it floating in or slightly emerged in shallow water with round leaves that have a “v-shape” opening or cleft.

Unlike native waterlilies which have white flowers (Nymphaea odorata) or yellow flowers (Nuphar variegatum), most exotic waterlilies have brightly colored flowers including pink, purple, and red. Exotics may also have white or yellow flowers and can be difficult to distinguish from native species. Individual flowers have numerous petals and may bloom all summer. Some varieties may or may not have seed for reproduction but they spread easily and extensively through their root system.

To easily control a water lily infestation, we recommend the Open Water Kit®. If you have any questions or would like to speak to us about water lily control, please feel free to call us at: 1-877-428-8898

Brittle Naiads

Brittle Naiad originates in Europe, Turkey, North Africa, India and Japan. It was introduced into the United States in the 1900’s. It often grows with other submersed aquatic plants such as southern naiad, pondweed, coontail, and watermilfoil. Brittle Naiad’s preferred habitats include shallow water along lake shores, sheltered lake inlets, ponds, and streams with slow currents.

For controlling of the growth of the aquatic weed Brittle naiad in Minnesota ponds and lakes we recommend the use of RestoreAccess Ultra or Hydrothol 191.