Have you ever looked out at a pond and noticed the surface was covered in something green? Don't mistake this for fronds, algae or toxic waste. It may just be duckweed, tiny oval-shaped plants on the water's surface. These plants can cause some problems, but they also have benefits.
Duckweed belongs to the Lemnaceae family, a group of the smallest flowering plants with no leaves or stems, though some have roots. All duckweed varieties can produce small flowers, but they rarely do.
Duckweed mainly grows in warm, wet environments around the world, either in shade or direct sunlight. It floats, forming a blanket over small bodies of slow-moving water. These bodies of water contain high levels of nutrients such as phosphorus or nitrogen.
Duckweed is a source of food for water fowl and even people in parts of Southeast Asia such as Thailand. It also provides shelter for pond animals, such as bullfrogs. It can be placed in freshwater aquariums.
Duckweed can multiply at an incredibly fast rate. It can cover the surface of a body of water, blocking sunlight and killing fish and aquatic plant life. This growth also can clog outlets such as water drains.
Using herbicides to kill an overgrowth of duckweed is ineffective because duckweed thrives on the nutrients in the water. To control the growth of duckweed, reduce the flow of nutrients into the water or remove the duckweed at repeated intervals.
Duckweed can be used to help purify water by controlling algae growth and converting waste and sewage water into treated water and biomass (duckweed leaves and roots). However, it can't process toxic substances such as heavy metals and pesticides.
Duckweed also reduces water evaporation and keeps water cool.