What are duckweeds?

Duckweeds are the fastest growing plants in the world and the tiniest flowering plants on Earth. They are often mistaken for algae growing on water bodies. They are aquatic plants found worldwide in temperate and tropical places. They make exact clones of themselves very quickly and can double in biomass in as little as 16 hours and form large populations, taking over water courses in peak growing seasons. 

Duckweeds are commonly found in stagnant waters, ponds and swamps and canal networks. They are important for biodiversity: ducks eat them, frogs hide under them,  and birds and other animals can transport them great distances. A healthy coverage of duckweed can control algae populations in water as they form a mat on the surface, excluding light from deeper penetration in a water body.

 Common duckweeds (Lemna minor) cover the expanse of the UK and are super common. The fat and ivy-leaf duckweeds are also frequently found species in the UK. The least duckweed is an invasive alien species introduced initially from America to Europe and then to the UK, this species is currently migrating Northwards.  Greater duckweeds are  the largest and have many short stubby roots. The smallest of all UK duckweeds, the rootless duckweed has been reported present in the South of the UK. Species use multiplication as clones as their primary means of reproduction to ensure fast growth and large populations. Many species also produce miniature flowers in Summer and others make 'overwintering seeds' called turions which sink to the bottom of water and transform again into duckweeds in Spring.  Image taken from Collins flower guide: Guide to the flowers of Britain and Ireland.