How to Get Rid of Duckweed

by Admin

In this class I will teach you how to get rid of duckweed naturally in a pond and preventive measure for duckweed control.

What is Duckweed?

“Duckweed” or sometimes called “bayroot” is an aquatic plant that floats just below or on the surface of slow or still fresh water.  It is  a tiny, green, leafy plant usually similar in structure to a lily pad.  As with a majority of aquatic plants, duckweed grows best in an environment that is high in phosphate and nitrogen.  As they grow and float along the surface duckweed will absorb these nutrients.

How to Get Rid of DuckweedYou’re going to have to consider whether or not you want to try to control a duckweed infestation or eradicate it.  Duckweed can be hard to completely eliminate as it can be reintroduced by waterfowl or seeds that are germinating below the surface.  It also can serve an important function in your pond as a food source to water fowl, herbivorous fish, insects and microorganisms.  When considering to remove or control duckweed you have three choices: herbicides, biological controls and mechanical controls.  I always suggest you try natural techniques to get rid of duckweed before trying a herbicide.  Speak to a professional about herbicides and whether or not it’s right for your situation.  Most of the time you can talk to your local Department of Natural Resources and get some free advice.

Duckweed Control with Herbicides

Herbicides are substances that have been found to kill a particular type of vegetation.  Some are selective and will only kill particular plants while others may wipe out all vegetation.  Some are hazardous to humans and wildlife while other are quite benign.  I think herbicides are the least optimal way to remove duckweed and deciding what herbicides are safe can depend on where you live and the surrounding wildlife.

Duckweed is classified as monocots so most broad leaf herbicides are usually noneffective.  Diquat and sonar have been found to be effective in removal.  Once again before using herbicides I would try other methods or consult with a professional.

Mechanical Controls

Duckweed can be harvested using mechanical devices.  It’s a simple, fast and effective means to control duckweed.  The downfall is you may have to do it several times a year, but I think this is a small price to pay when trying to conserve a natural ecological environment.  You can use the harvested duckweed as an edible protein for fish, cattle or used as a fertilizer in your garden.

To harvest you can simply use a fine net and drag it on top of the water or you can purchase or build a mechanical skimmer.  Both options are highly effective but you will leave some duckweed behind requiring future harvesting.  If you’re using the harvested duckweed this may not be a bad thing.

Biological Controls

Certain herbivorous fish, waterfowl, insects and microorganisms can be used to control a duckweed population.  The benefits are longer term control, relatively low cost, and avoidance of chemicals.  The disadvantages are the lag time before you begin to see an effect and availability of agents available in your area for controlling duckweed.

Duckweed Prevention

I always think the most logical way to control any situation is to take preventive measures.  It is going to be very difficult to ever completely remove duckweed as it will continually be reintroduced by animals and waterfowl.  However, these simple techniques will help control a population.

Aeration – Aeration uses a pump to blow oxygen into a pond similar to a fish tank is oxygenated.  Constantly circulating the sediment at the bottom of a pond from run off and decay, will help restore the ecological system of the pond and bring back new life that will feed on the duckweed.  This can be very effective but may take a few seasons to work.

Nutrient Reduction – Try to prevent fall debris, field run-off and other debris that upsets the balance of a pond.  Also try to prevent using fertilizer and other chemicals around or near your pond.  Overtime this will help restore the natural balance of your pond and the organisms that feed on the duckweed.


Always exercises responsibility and get expert advice when doing anything in mother nature.  Remember that duckweed is a natural process, so it is unlikely it can be completely prevented.  With some effort you can get rid of most of the duckweed and overtime bring it under control naturally.  I hope you enjoyed this class, make sure to share your experiences below.


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