How to prune trapa natans

Autumn, after seed harvest; thin in summer if overcrowded. Remove entire floating rosettes by hand or net to reduce density. After the growing season ends and plants die back, clear them from the water to prevent decomposition fouling the pond. Dispose of seeds carefully to prevent spread.

As needed in summer; full clear-out each autumn. Trapa natans (water chestnut) needs no pruning for plant health. Thin or remove excess floating rosettes if they overcrowd a pond, blocking light from submerged plants. After harvest in autumn, remove dying plants entirely. Note: it is invasive and banned in several US states — check local laws before growing.

Remove entire floating rosettes by hand or net to reduce density. After the growing season ends and plants die back, clear them from the water to prevent decomposition fouling the pond. Dispose of seeds carefully to prevent spread.