Duckweed is a flowering, aquatic plant that floats on the surface of the water in wetlands and slow-moving bodies of fresh water. Duckweed is a very small plant with one to three small fronds. It is light green and one of the very smallest flowering plants. It can practically double in size in just 16 hours, if the growing conditions are ideal. Duckweed got its name from the plant being transported on duck's feet when they traveled from pond to pond.