I stop fertilizing my pond plants at the end of August. I figure that when the daylight hours get short and the sun is at low angle much of the day and the leaves slow down growing, the plant is getting ready for winter.

Perhaps someone who grows water lilies and other pond plants professionally could comment on when they stop fertilizing.

Thanks kalevi.

I also stop fertilizing at the end of August as the plants are starting to slow down at that point.