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. Duckweed in ponds is frequently misidentified as algae. Once established, duckweed in ponds 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. If you need to begin duckweed control, read below.
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.
There are several options to control duckweed in ponds.
- Use a season long herbicide such as Sonar™ A.S.. One treatment treats duckweed and many other common pond weeds for the season.
- 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.
- 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:
- When beginning duckweed control, treat your pond in sections. Treat only half the pond's surface at a time. During hot weather or when treating heavy growth, it is important to treat no more than ¼ of your pond at a time and wait the full 14 days before re-applying. This helps lower the risk of fish loss during hot weather or when treating heavy growth.
- 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.
- Take a proactive approach to pond management. Use PondClear™, MuckAway™ and Pond Dye to keep your pond looking great. For more information, see our article on the Airmax® Ecosystem™
Ask an Expert
If you are unable to identify your pond weed(s) using our Weed ID Guide, follow this article to email us a photo.