Myriophyllum

Myriophyllum is a genus of aquatic plants in the family Haloragaceae, commonly known as watermilfoils. These plants are found in freshwater habitats worldwide, from still lakes to slow-moving rivers, and are often prominent in submerged or marginal zones. They are characterized by slender stems and finely divided, feathery leaves that are typically arranged in opposite or whorled patterns along the stem.

The genus comprises around 60 species. Leaves are usually pinnate or tripinnate with threadlike leaflets, giving a delicate, feathery appearance. Some species produce winter buds, or turions, that help them survive seasonal changes. Reproduction occurs both by seeds in some species and, more commonly, by vegetative fragmentation, which enables rapid spread in suitable conditions.

Ecology and uses: Watermilfoils provide habitat and food for aquatic invertebrates and fish, contribute to oxygen production, and help stabilize sediments. They can influence light penetration and water chemistry in their environments. Many species are valued as ornamental plants in aquariums and water gardens for their ornamental foliage and dense growth, with species such as Myriophyllum aquaticum (parrot’s feather) widely cultivated.

Invasive status and management: Some Myriophyllum species, notably Myriophyllum spicatum (Eurasian watermilfoil), are invasive in parts of North America and other regions, where dense beds can displace native vegetation and impede recreation. Management approaches include mechanical harvesting, selective herbicides, and, in some areas, biological control using milfoil weevils or other natural enemies.