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Overwintering Tropical Water Lilies

by Andy Lohaza

Article in OWGS October 2004 Newsletter

The tropical water lilies need as much a rest in the winter months as do our hardy lilies, although the coldness of our climate will ultimately be their death. So the dormancy they require will be a little different.The tropical water lilies will begin to shut down as the water temperatures start to fall and light levels start to decline.   Fertilizing should have stopped by mid September (for zone 5 this year) as with all water plants containerized in the pond. Doing so for the tropical water lilies has a specific effect; it promotes the growth of small tubers/corms to store energy for the winter ahead. These small tubers/corms are joined to the mother plant and can be successfully broken off to produce new plants for the next season. It is important to maintain an ambient temperature of around 60ºF for the tropical water lily to survive the winter storage. These are the methods that worked for most people and can be modified for your own situation. Method 1 The wash and store method 1-Remove the water lily from the pond and remove all the soil around the plant, washing it all away to expose the root mass and tuber/corm. 2-If small tubers/corms are produced, remove these and place in damp sand in a glass jar for storage (you may like to dust them with a fungicide before placing them in storage) 3-Remove the full-grown leaves off the mother plant and trim away excess roots. 4-Place the mother plant (dusted with a fungicide) in some damp sand also and keep in an area of the house that will stay above 60ºF. 5-Come spring next year, awaken your stored plants by potting them up in fresh soil with fertilizer tabs of your choice and place in your pond, 2-4" below the water surface to get them excited, once the temperatures are safely maintained around 60ºF. 6-When they start to grow once again, place them in the appropriate spot in the pond where it can be enjoyed for another season. Method 2 I have the room to store indoors! 1-;Bring in your entire tropical water lily from the pond, pot and all intact! 2-Trim off the largest leaves and any damaged leaves so the pot fits into an aquarium or lined pond inside. 3- Keep the temperature above 60ºF to keep the plant alive. 4- Here you have 2 choices: a) Let the water slowly evaporate over the winter, (which is their natural dormant season) and add warm water in the spring when you are ready to start growing the plant again. (This method is employed by Heinjo Lahring, IWGS member from Alberta) Or b) Some supplemental lights may be required to give it a little more energy over the lower daylight hours/ daylight intensity of our winters, to keep the plant growing. 5-Come springtime when the temperatures and water warms up, you may repot the tropical in some fresh soil, add your fertilizer and place in the pond where it can be enjoyed for another season.   Now my own personal experience has been with the first method, however, I did modify the way I did it. After washing the soil from the roots of the plant I let the entire plant dry out, all the leaves and roots intact, on the garden bench indoors - out of direct sunlight. I believe this let any stored energy make its way back into the core of the plant and makes the clean up a little easier.   I let it dry for about 3 days, then remove the dried leaves and trim off the finer roots. I had the luck of finding some tubers/corms and potted them up in 4" pots for winter - I had the room! The small plants I grew on in an aquarium at a warmer temperature with lights, and the mother plant was repotted and placed into a pail of water under the bench. Over the course of the winter I changed the water every other week then in spring, brought it out, fertilized it and replaced it in the pond. I did not use a fungicide on these plants (and lost some of the small tubers/corms I removed due to rot). I live in zone 6b. In the southern United States, the water gardeners are able to leave their potted tropical water lilies in the pond; they just move them to deeper water like we do our hardies for the winter. Good luck with trying out these methods! Don't forget to ask the other members at the meetings what they do - some have better success with methods that are rather different