Many know, but few know by name, the Purple Loosestrife. This somewhat woody plant lives on the banks of almost all biological pools since it is indifferent to the mineral composition of soil and water. It is much appreciated for its long flowering of purple flowers that starts late in the spring but lasts until September. Among the adepts of this plant are not only the owners of biological pools but also many species of insects, especially butterflies.

The genus Lythrum, to which belongs the Purple Loosestrife, includes a series of species, all adapted to live on the banks of biological pools.