Tropical lilies are usually treated as an annual. They will continue to grow and produce blooms until the temperatures fall 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 at 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 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 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.
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