Waterscapes 101 Knowledge Base

Duckweed & Watermeal– Managing Floating Pond Weeds

Duckweed and watermeal are floating weeds that reproduce VERY FAST! One week a pond has some growing along the edges, and the next, the whole pond is covered. Besides looking HORRIBLE, complete surface coverage by weeds can lead to a fish kill.

Take a closer look. Before selecting an herbicide treatment, confirm the weed species by pulling a sample from the pond. Duckweed and watermeal can be confused with surface algae. Duckweed is about ¼- ½” across and has 3-4 leaves, making it look like a miniature 4-leaf clover. Watermeal is round/oval shape and the size of a pin head.  It is possible to have duckweed and watermeal growing together.


Where does duckweed and watermeal come from?

These pond weeds are commonly found throughout the United States. Due to their size, it is easy for a plant to attach to the body of waterfowl visitors  traveling from pond to pond. Once relocated, the plant begins to multiply. Each plant is able to create a sister plant every 24 hours. After 30 days, 1 harmless plant is now over 1 billion individual plants (literally).

When water temperatures drop in fall/winter, plants mysteriously disappear. Duckweed and watermeal go dormant and drop to the pond bottom when the water temperature drops in the fall. They re-emerge to the surface in spring when the water temperature increases! 

Due to the incredible speed of growth, duckweed and watermeal are difficult to manage. Your Creating a “treatment cocktail” significantly improves the outcome of the herbicide treatment. This “cocktail” is our Duckweed Destroyer Pack, which consists of Cutrine Plus, Tsunami DQ, and PlexMate. The TRICK is you need to kill ALL of the weeds. Leaving any living duckweed or watermeal will lead to regrowth. This is a rapid treatment, so results will be seen within 48 hours. Any vegetation that doesn’t turn yellow/brown within 48 hours should be re-sprayed.


Sonar AS or RTU, as well as Propeller are other treatments available for complete surface treatment of duckweed and watermeal. These both yield excellent results, but can only be used in ponds with little to no flow through. 

It is vital to have aeration when treating the pond with chemicals. As weeds die, they consume oxygen from the water. Increasing oxygen levels will lower the risk of a fish kill during chemical application.

Make sure you know your pond size! Proper dosing is important. If you don’t know your pond size- our experts can use our mapping software to determine the surface area of your pond.

How long will this pond treatment manage the weeds? 

These treatments kill the current growth that is present at the time of application. If there is a nearby pond with duckweed or watermeal, it is possible for re-introduction at some point. If any new growth is spotted, treat them immediately or remove them with a skimmer net before they have a chance to multiply.

Note: Pond dye will not help control duckweed or watermeal as it does for algae or submerged weeds. 

Products to help with Duckweed

Waterscapes 101

The Knowledge Base for Pond and Lake Management