Ludwigia grandiflora, the water primrose, is an aquatic plant of the order Myrtales.

[3] The two species can be distinguished at a chromosomal level, because L. grandiflora is hexaploid and L. hexapetala is decaploid.

[9] It is introduced to warm temperate areas of North America, Japan and Europe and has formed large stable populations, particularly in France.

[10] As of summer 2024, the Portuguese city of Arganil announces measures against the species in its river Alva.

A study in Belgium, where L. grandiflora is introduced, showed that the flowers are visited by a wide variety of insects including bees, Lepidoptera, beetles and hoverflies.