Common duckweed is native to Asia, Africa, Europe, and North America. Lemna
means "water-plant" and "minor" means "lesser"—lesser because there is a similar-appearing plant
in a different genus and with larger leaves, greater duckweed.
Identification: Duckweed forms a nearly continuous
mat of tiny green leaves just below the surface of freshwater ponds and slow-moving streams. The
leaves are so small that colonies resemble algae or "pond scum" from a distance. Each leaf
is oval, 1/32-¼″ (1-8 mm) × 1/32-⅛″ (0.6-5 mm), equipped with tiny air sacs for flotation.
Flowers are rare and nearly invisible at
about 1/32″ (1 mm) in diameter. Fish and birds benefit from its relatively high fat and protein
levels: "duckweed" is named for ducks' preference for this food.