Duckweed, from the plant family Lemnaceae is a family of flowering plants, known as the duckweed family, as it contains the duckweeds or water lentils. The duckweeds are now known to be a branch of the arum or aroid family (Araceae), These plants are very simple, lacking an obvious stem or leaves, but consist of a small 'thalloid' or plate-like structure that floats on or just under the water surface.
In the photo to the right, the larger Duckweed is surrounded by its more prolific cousin, Watermeal
To give you example of the sizes of each plant, the smaller watermeal shown in the photo is about the size of corn meal. Which makes Duckweed about the size of a pencil eraser. Duckweed is commonly a secondary, less prolific infestation but just like Watermeal, indicates declining pond health due to an overabundance of nutrients.
Duckweed, from the plant family Lemnaceae is a family of flowering plants, known as the duckweed family, as it contains the duckweeds or water lentils. The duckweeds are now known to be a branch of the arum or aroid family (Araceae), These plants are very simple, lacking an obvious stem or leaves, but consist of a small 'thalloid' or plate-like structure that floats on or just under the water surface. 
