HARDY WATER LILIES
With the lower temperatures during the fall season, you will notice a decrease in water lily blooms, as well as lily pads turning yellow as the water temperatures lower. It is important at this time to remove the dead leaves and spent blooms, to avoid having the debris in the pond over winter. As winter approaches and water temperatures drop, the water lily will go dormant. Remove all the dead lily pads and lower the potted lily to the deepest part of the pond, or to a water depth of about 2 feet.
TROPICAL WATER LILIES
Tropical lilies are usually treated as an annual. They will continue to grow and produce blooms until the water temperature falls below 60 degrees. If you choose to try over-wintering your tropical water lily, moving the potted plant into a greenhouse is the most successful. Another method is to re-pot the lily in a 6" pot and place the lily in at least a 20 gallon or larger aquarium. Keep the water temperature between 70-75 degrees. You will need a fluorescent grow light to provide 10 to 12 hours of artificial sunlight per day. Do not fertilize the lily at this time, as you will not want to encourage any new growth. Simply keep the plant alive until temperatures are warm enough in the spring to move the lily back outside to the pond. There is one other option for you to try if you are determined to save your tropical lily for the next season. Starving the plant in late summer (do not fertilize) will cause the lily to form tubers in the fall. Once the leaves have died off, remove the tuber that has formed under the crown. Wash it thoroughly and air dry for a few days. Remove any roots still attached, wash thoroughly again and place in a jar filled with distilled water or slightly moist sand. Store the container in a cool, dark place at approximately 50 to 60 degrees. Check regularly to make sure the sand is moist, or if storing in water, that the water has not turned foul or discolored. If it has, replace it with fresh distilled water.
As the lotus leaves begin to turn brown, the lotus is beginning to go dormant for the winter. Do not cut off the leaves; allow them to die back naturally. At this point it is safe to cut them above the water line. You do not want water going down the hollow green stem and having it get into the air channels of the tuber. If this happens you risk drowning the tuber and cause it to rot. Make sure the potted lotus is below the ice. Allowing the tuber to freeze may kill the plant.
As long as the submerged plants are below the ice, they will usually survive the winter. Any part of the plant that is allowed to freeze will turn to mush and add unwanted debris to the pond. It is wise to cut these plants back and sink them below the surface.
HARDY BOG/MARGINAL PLANTS
Once your hardy marginal plants begin to brown, usually after the first hard frost, prune back excess foliage and discard any decaying material, so it does not compromise the water quality over the winter months. Potted bog plants such as Pickeral, Thalia Dealbata and Japanese Variegated Iris should be placed at a sufficient depth to avoid freezing the crown of the plant. Most of the other hardy bog plants can be left as they are and will return the following spring.
TROPICAL BOG PLANTS
Many of the tropical bog plants will winter well indoors in a sunny window or with a grow light. They do not need to be submerged in water. Keep the soil constantly moist by placing the potted plants in a tray of water.
Floating plants such as Water Hyacinth and Water Lettuce are considered tropical and will not survive temperatures below freezing. After the first hard frost, remove floating plants from the pond to prevent them from decaying and adding unwanted debris to the pond.