Watermilfoils stand their ground in competition with other plants

Watermilfoils Myriophyllum spp. are perennial vascular plants found in both fresh and brackish waters. They are common on almost all soft bottoms in the Baltic Sea, but thrive best in sheltered and nutrient-rich areas. They grow attached to the bottom sediment and cannot withstand very large waves. Like other vascular plant communities, watermilfoils provide shelter for many invertebrates and young fish.

Watermilfoils grow quickly and reproduce easily from stem fragments, which is why they often take over areas in bays disturbed by dredging or boat traffic, for example. Watermilfoils also benefit from eutrophication. However, prolonged eutrophication and the resulting turbidity of the water can also impair their growth.

Watermilfoil dominated bottoms will also be preserved in the future

Watermilfoil dominated plant communities occur most frequently on shallow and well-protected muddy bottoms, but also to some extent on open mixed bottoms. Myriophyllum bottoms are classified as least concerned habitats; the habitat is not expected to decline significantly in the future.

Watermilfoils of the habitat include four species: spiked or Eurasian watermilfoil (M. spicatum), shortshipike, northern or Siberian watermilfoil (M. sibiricum), whorled watermilfoil (M. verticillatum) and whorl-leaf or whorled watermilfoil[ (M. alterniflorum). The rarest of these on the Finnish coast is M. alterniflorum, which is most clearly a species of unfertile, oligotrophic lakes. Watermilfoils can form either monospecies stands or mixed communities with other vascular plants, such as pondweeds (Potamogeton spp., Stuckenia spp.) and buttercups (Ranunculus spp.).

Species of watermilfoil habitats

Eurasian watermilfoil (Myriophyllum spicatum)

Siberian watermilfoil (Myriophyllum sibiricum)

Perfoliate pondweed (Potamogeton perfoliatus)

Sago or fennel pondweed (Stuckenia pectinata)

Autumnal water-starwort (Callitriche hermaphroditica)

Horned pondweed (Zannichellia palustris)