To date, estuarine ecosystem research has mostly neglected silica cycling in freshwater intertidal marshes. However, tidal marshes can store large amounts of biogenic silica (BSi) in vegetation and sediment. BSi content of the typical freshwater marsh plants Phragmites australis, Impatiens glandulifera, Urtica dioica, Epilobium hirsutum and Salix sp. was analysed year-round. All herbaceous species accumulated silica in their tissue during their life cycle. Of the live plants, P. australis contained the most BSi (accumulating from 6 to 55 mg g–1). Dead shoots of P. australis had the highest BSi content (up to 72.2 mg g–1). U. dioica ( ; To date, estuarine ecosystem research has mostly neglected silica cycling in freshwater intertidal marshes. However, tidal marshes can store large amounts of biogenic silica (BSi) in vegetation and sediment. BSi content of the typical freshwater marsh plants Phragmites australis, Impatiens glandulifera, Urtica dioica, Epilobium hirsutum and Salix sp. was analysed year-round. All herbaceous species accumulated silica in their tissue during their life cycle. Of the live plants, P. australis contained the most BSi (accumulating from 6 to 55 mg g–1). Dead shoots of P. australis had the highest BSi content (up to 72.2 mg g–1). U. dioica (