Duckweed Treatment


Duckweed is a floating plant that infests the surfaces of ponds and may cause extreme damage to the health of underwater life. Seeking and implementing treatment for duckweed infestations ensures the health of your home pond. Familiarize yourself with how to avoid duckweed and what to do when it shows up through reliable control methods.


Duckweeds belong to the Lemnaceae family and float freely on pond surfaces in the home garden. Duckweeds are green in color and most often appear as the Lemna species with weeds that reach up to 5/23 inch in width, according to the Iowa State University Extension. Duckweeds do not display true foliage, but appear as round, flat plants.


Through reproduction referred to as budding, new buds appear daily, so duckweed may cover the surface of a pond within as little as two weeks, according to the Ohio State University Extension. When duckweed covers a pond, it blocks out necessary sunlight that plants and aquatic animals depend on for photosynthesis, the conversion of sunlight into energy for plants. The plants that live within a pond produce oxygen that the aquatic plant and animal life need for survival. Excessive duckweed decreases pond oxygen levels and threatens pond life.

Pond Care

Floating roots that dangle beneath duckweed absorb nutrients from ponds. Rapid infestations occur due to excessive nutrient content in ponds caused by cultural issues like fertilizer run-off and drainage from livestock feed, according to the Ohio State University Extension. To control the nutrient buildup that attracts duckweed and causes subsequent problems, consider using bubble aeration. With bubble aeration, a shore-based compressor creates bubbles in the bottom of your pond that lift accumulated nutrients where pond life can consume them before levels become dangerous.

Natural Control

For natural control of a duckweed problem, an inexpensive treatment is the physical removal of duckweed. As soon as you notice a problem, wait for duckweed to gather on one side of the pond for easy collection. Remove the duckweed from the water with a mesh net, advises the Ohio State University Extension. Or, consider releasing koi fish into your pond as a preventive natural treatment. Koi eat duckweed and, if present before an infestation exists, they will keep the duckweed from taking over.

Chemical Control

When other treatment options are not working, turn to chemical control. Apply a chemical with the active ingredient diquat in a 50:1 ratio mixture with water at a rate of 1 gallon for every acre of the surface area of your home garden pond, according to the Ohio State University Extension. Spray this herbicidal treatment on duckweed either as collected groups or for the treatment of a single weed, depending on the progression of the problem. Duckweed populations begin to decrease within a few days to a week.

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About this Author

Tarah Damask's writing career, beginning in 2003, includes experience as a fashion writer/editor for Neiman Marcus, short fiction publications in "North Texas Review," a self-published novel, band biographies, charter school curriculum, and articles for eHow. She has a love for words and is an avid observer. Damask holds a Master of Arts in English and creative writing from the University of North Texas.