To ready your pond for winter, start by adding your last dose of fertilizer in August. In September you should tend to all of your plants by removing and pruning all dead foliage. Do this for all plants.
For hardy waterlilies, after pruning dead foliage and cutting back, place the container with the crown of the plant beneath the freeze line.
Cut your lotus stems above the water line as lotus stems are hollow and you will drown the plant if the stems are cut beneath the water line. Prune and remove all dead foliage. Place your lotus container so that it is beneath the frost line.
All tropical waterlilies should be removed from the pond after the first frost. Once all of the dead foliage is removed, cut the foliage back. It is then time to separate the tubers from the soil, wash the tubers and treat with a mild fungicide. You may store your tubers indoors, in temperatures between 50-55 degrees in damp sand. By the middle of February, stored tropical waterlilies can be planted in small pots with 3" of water above the soil and placed in a sunny location indoors. These waterlilies will have to be re-potted in the spring before putting back in your pond in the spring/summer.
Tropical waterlilies are often treated as annuals and replaced the following year.
You may bring indoors and use as a house plant or treat as an annual. Most tropical plants require lots of sunshine, so place your plants in a sunny location!
Treat as an annual
Place your oxygenators beneath the frost line. You can do this by placing them on the floor of the pond.
Clean out any debris, branches or leaves that may have fallen into the pond. You may decide to place a net over your pond to keep debris and leaves from falling into your pond over the winter months. Also consider the use of a pond heater during the winter months, this will allow harmful gasses to escape through a hole in the ice. Pond heaters will kick on when the temperatures go below 32 degrees. Many pond heaters are energy efficient.
At this point, your pond should be ready for winter!