How to Fertilize water fern?
Balanced perennial feed every four weeks from spring through summer

water fern · Azolla filiculoides
Also known as: fairy fern
This plant is listed on Schedule 9 of the UK Wildlife & Countryside Act as an invasive non-native species. Across the EU, UK and NI it is an offence to plant or cause to grow in the wild plants listed on Schedule 9 of this order. These plants should not be planted or caused to grow in the wild and in addition are banned from sale. Gardeners possessing them should undertake measures to control them. See RHS advice on invasive non-native species for further information
Balanced perennial feed every four weeks from spring through summer