is a species of aquatic plant
known by the common name pond water starwort
. It is native to Europe but it is present on other continents as an introduced species
and sometimes a noxious weed
of waterways. This is an annual herb rooting to the substrate in shallow water or in mud alongside water bodies. Slender stems reach to the surface and form floating mats of leaves, which are often round to spoon-shaped but are variable in morphology. The plants are monoecious
, with male and female flowers on an individual. Both types of flower are very tiny and whitish in color.