Overwintering Your Aquatic Plants

With proper care, and some luck, your aquatic plants should have provided you with much enjoyment during the summer. Fall is the time to prepare these plants for overwintering. If you follow the recommened procedures, you will be rewarded with more mature plants that show improved performance next year.

Hardy aquatic plants can be left in the pond over the winter and will do just fine provided they have proper water cover and snow protection. Examples are hardy calla (Calla Palustris), Bob bean (Menyanthes Trifoliate), and marsh marigold (Caltha Paluithrs).

Tropical aquatic plants will not survive in our climate if left outdoors over the winter. There are two options: replace them in the spring or take them indoors. Parrot feather (Myriophyllum Proseysinacoides) is not expensive and is a very vigorous grower, so it can easily be replaced in the spring. Portions of the plant can be taken indoors and kept in an unheated aquarium with a grow light. The portions can simply be floated in the aquarium over winter and then repotted in the spring. Cambomba (Cambomba caroliniana) and elodea anacharis (Elodea canadensis) can be treated the same way, or the entire plant taken indoors and kept in an unheated aquarium.

Water hyacinth (Eichlornia Crassipe) and Water lettuce (Pistia Stratiotes) will not survive a hard frost. These are inexpensive, prolific plants that can easily be replaced. If you do want to keep them over winter, take them indoors before a killing frost hits. Try using an unheated aquarium with a grow light, but don't keep large gold fish in the aquarium as they will eat the plants, which will eventually die. .

Water poppy (Hydrocleys Nymphoides), a potted plant, can be taken indoors and kept in a container filled with 5-7.6 cm (2-3 in.) of water in a well lit location. Or it can be kept in an unheated aquarium with a grow light with approximately 5 cm of water over the top of the pot.

Floating heart (Nymphoides Peltata) is an inexpensive plant that is a vigorous grower. The potted plant can be treated the same as the water poppy.

Dwarf papyrus (Cyperus Haspans), arrowhead (Sagittaria Latifolia) and umbrella palm (Cyperus alternifolius) will do very well as houseplants provided you keep them very moist (wet) in a well lit location.

Iris Pseudacorus can be taken out of the pot and simply planted into the perennial border into fertile moist soil and then repotted in the spring. Mulching it well for the winter and providing adequate snow cover will assure the survival of this hardy plant.

Hardy water lilies should not be left outdoors over winter unless your pond is deep enough to prevent freezing. There are several methods for keeping them over winter but the most successful is as follows: Remove the potted lily from the pond and allow it to drain for a few hours in the shade. Take any debris from the pot and remove the leaves. Wrap the pot in wet burlap and then a black garbage bag, and store it in your basement. Check it periodically during the winter (every 2 weeks) to ensure that the soil is moist, adding water if it appears to be drying out.

In the spring, fertilize it and place it back into the pond. With some experience water lilies can be kept over winter for years.

Garry Miller is a landscaper who specializes in aquatic gardeing. He is also a student in the Extension Division's Master Gardener Program at the University of Saskatchewan. This column is provided as an extension service by the Extension Division and the Department of Horticulture Science, University of Saskatchewan.
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