Duckweed is a free-floating water plant that spreads rapidly. It is considered a nuisance plant in many areas of the country. They are the world's smallest aquatic plant.
Duckweed has one to three light-green leaves that measure 1/16 to 1/8 of an inch across. Hairlike roots are attached to the leaves. Common duckweed (Lemna minor) is smaller than giant duckweed (Spirodela polyrhiza). Watermeal is the smallest of all duckweed.
Duckweed forms dense colonies in nutrient-rich stagnant water. It does not grow in moving water, but prefers still water.
A duckweed plant produces a daughter bud about once a day. With ideal growing conditions, the original plant and its daughter buds can produce as many as 17,500 plants in two weeks.
A duckweed colony blocks the sunlight, which results in the decline of underwater plants. It also depletes the oxygen in the water, which causes fish to die.
Duckweed is difficult to control. Reduce the runoff of nutrients into bodies of water and use bubble aeration to inhibit the growth of duckweed. Duckweed can be removed manually or controlled with chemicals. Koi, goldfish and grass carp eat duckweed, but grass carp will eat other plants first. Although ducks eat duckweed, they also spread it when it sticks to their feathers.