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Duckweed is a very small floating plant. It has shoe-sole shaped leaves with a small hair-like root hanging below. It resembles a four-leaf clover approximately the size of a pencil eraser. It is frequently misidentified as algae. Once established, it can cover the entire water surface and resemble a golf course green. It can cut off sunlight to submersed plants and cut off oxygen to fish and other wildlife.

Mechanical Control

Duckweed can be controlled by raking or skimming it off the pond's surface.

Duckweed typically prefers stagnant and slow moving water. By adding an aeration system, you can eliminate Duckweed completely or limit the growth to the edges which are easily reachable with a hand skimmer.

Chemical Control

There are several options to control duckweed.

  1. Use a season long herbicide such as Sonar™ A.S.. One treatment treats duckweed and many other common pond weeds for the season.
  2. Use a broad spectrum contact herbicide, such as Ultra PondWeed Defense®, will quickly kill duckweed. Because it does not stay in the water body, multiple treatments may be needed throughout the season.
  3. Use Clipper™, a fast and selective herbicide that controls tough invasive and nuisance aquatic plants.

Chemical Application Best Practices

Anytime you use chemicals treat weeds and algae, please keep in mind the following:

  • Treat your pond in sections. Treat only half the pond's surface at a time, if the weather is hot, only treat 1/4-1/3 of your pond. Wait 10-14 days between treatments.
  • Once the weeds have browned, use a rake to remove as much dead material as possible. This prevents an accumulation of dead plant material and muck.
  • Treat your pond with the proactive approach to pond management. Use PondClear™, MuckAway™ and Pond Dye to keep your pond looking great.