Look:
Le.Loup.Gris, Salvinia natans (habitus) 2, CC BY-SA 3.0
Salvinia natans is a fast-growing annual floating plant. It floats freely on the water surface and does not anchor itself to the bottom like other plants with roots.
The common floating fern can grow to a height of 3 cm and a width of up to 10 cm. The stems of the plant are branched and float horizontally in the water. Each stem has three light green leaves on each stem node.
The plant has developed two of its leaves as floating leaves. Their upper side is hairy and highly hydrophobic, i.e. water-repellent.
The third leaf of the plant, on the other hand, is under water and looks like a tuft of roots. However, as a Salvinia species, the common floating fern is rootless, with the submerged leaf taking over its function.
Between August and October, the sporocarps (spore fruits) develop on the root-like underwater leaves. These survive the winter while the plant dies. Young plants emerge from the sporocarps in spring. Salvinia does not form flowers.
Distribution:
Salvinia natans is native to Europe and Asia and mainly inhabits standing water, ponds or pools.
In Germany, the species is very rare and is threatened with extinction. It is under special legal protection, so it is forbidden to take Salvinia natans from nature.
Salvinia natans is often mistakenly confused with Salvina molesta or Salvina auriculata. In contrast to the last two species, the common floating fern is also found in Europe.
husbandry conditions:
Salvinia natans shows optimal growth under conditions with the following water parameters:
In addition, the common floating fern needs a lot of light and nutrients. Light, chlorotic leaves are a sign that the plant is lacking in micronutrients. In this regard, an additional supply of special fertilizer is recommended. With sufficient light and a good supply of nutrients, the floating plant grows and multiplies fairly quickly.
The common floating fern can be propagated by dividing the side shoots or by sowing the spore fruits.
Salvinia natans is also ideal for outdoor pond planting. The location should be sunny to semi-shady. The plant tolerates light frosts, but it is not hardy.
In order to be able to enjoy the aquatic plant for more than one season, overwintering is possible. For this purpose, the common floating fern is taken out of the pond with the landing net in autumn. He is then overwintered in the house, greenhouse or conservatory, warm and bright.
Particularities:
Salvinia natans offers small fish or animals protection between the root-like underwater leaves and also shades the ground with them. It is therefore ideal planting for Tadpole Shrimp, shrimp and small fish, which find suitable hiding places in it.
If necessary, the common floating fern can be easily collected from the water surface. For example, if it takes away the light from the bottom plants in the aquarium or spreads too much in the pond.
However, the floating plant can also help to combat algae. It does this by casting shadows on parts of the aquarium or pond and consuming the nutrients in the water.