We've already told you about the famous sub-lacustrine forests of Lake Geneva and their role as a refuge for biodiversity in the aquatic environment...
Today, let's take a closer look at one of the species that make them up: Eurasian water milfoil.
Common in Lake Geneva, it has a reddish stem (or green for young shoots) and branched leaves. The leaves are soft green and finely divided like a feather. They are arranged on the stem in whorls, normally in groups of four. Each leaf is made up of 12 to 24 pairs of leaflets (also known as "segments"). The average distance between whorls is over 1 centimetre. They look like larch branches, but in an aquatic version.
Eurasian water milfoil is a native plant in the Haloragaceae family. Its stem is rooted in the sediment and can measure up to 6 metres. Near the water's surface, it branches and can continue to grow horizontally, producing spikes of emerging flowers from June to September.
The plant's rhizomes, roots and lower shoots can persist throughout the winter, enabling it to start growing relatively early in the season. This earliness, combined with rapid growth, gives Eurasian water milfoil a competitive advantage over other aquatic plants.
Although it thrives peacefully in the waters of Lake Geneva, some species of bird, such as the Red-crested Pochard, feast on it.
