Overwintering and Storing Aquatic Plants

Just before the first frost you should start preparing to store your aquatic plants for the winter, a process known as overwintering. The difficulty of this task depends on the type of plant you are wintering. Hardy water lilies and emergent aquatic plants are fairly easy to maintain, but caring for tropical water lilies is much tougher because of their tropical nature.

Hardy aquatic plants

There are several ways to store hardy water lilies and emergent aquatic plants, but some basic requirements must be met in all cases. Plants must go dormant and be kept that way by keeping them in a cool location (50 degrees maximum). They must not be allowed to dry out and their roots must not be allowed to freeze.

If you have a pond two or more feet deeper in some areas than the frost zone, overwintering hardy plants is a simple task. Trim off all the foliage and stems and drop the plants into the deepest area of the pond.

Plants kept in shallow ponds and container aquatic gardens will need to be brought in for the winter. For hardy water lilies and emergent plants lift the containers from the pond just after the first frost and leave them in their pots. Trim off all dead leaves and stems. Place the containers in plastic bags to retain moisture and store them in a basement or other area where the temperature doesn’t rise above 50 degrees or drop below freezing. Check periodically to make sure there is plenty of moisture in the bag. Maintain these conditions until spring.

Another way to overwinter these plants is to remove the rhizomes from the pots, prune all old leaves and stems, and store them in damp sphagnum moss placed in plastic bags. Store in an area that is cool (50 degrees) until spring.

Tropical aquatic plants

Storing tropical water lilies during cold weather is not easy and success depends on the variety you're growing. Tropical water lilies are divided into two types as far as procedures for overwintering go: egg-bearing (oviparious) lilies and live bearing (viviparious) lilies. Night-blooming water lilies tend to be egg bearing, while most day-blooming blue varieties are live bearing.

Night blooming water lilies are easier to winter because they readily form tubers to survive. Live bearing lilies do not tend to do this, but some do form plantlets at the junction of the leaf and petiole. These plantlets can be harvested, potted and over wintered in an aquarium.

Harvest the tubers of night blooming lilies by moving the plants to a cool dark place just before the first frost. Let the water lilies gradually dry over a few weeks then remove dried foliage and blooms. After you've cleaned the plants, carefully search the soil for the nut-like tubers or rhizomes. Remove them from the soil, trim off any remnant roots at the base and then, using a soft toothbrush, wash the tubers thoroughly and carefully.

Use damp peat moss to store these tubers. Soak the peat moss thoroughly, and then squeeze it until it holds its shape, but does not drip any more water. Fill a container with the peat and poke several circulation holes in the lid. It's a good idea to treat the tubers with a fungicide such as Captan and label them before layering them in the peat. Pop on the lid and put the container in a cool dark place that stays around 55 degrees. Protect the container from possible rodent damage. Check your lilies every so often to make sure they do not rot, or dry out. Keep the peat damp but not wringing wet.

When spring returns, repot your lilies and start them inside. This method may not work with larger water lily tubers because they are hollow in the center, and tend to slowly dry out over the winter.

You can also use an aquarium to winter tubers. Remove plants from the pond before the first frost, trim off excess foliage and roots and repot them into smaller containers. Place the pots in an aquarium in a sunny area and maintain the water temperature around 70 degrees. Even though your water lily will send up a few very small leaves, do not fertilize the lily during the winter. Bright light is critical. Place fluorescent lights directly over the water and use timers to make sure the plants receive 15 hours of light each day.

The distilled water method of wintering is yet another way to nurture your lilies during cold weather. Harvest the tubers as outlined above. Place the washed tubers in jars of distilled water and store them in an area that will remain around 55 degrees. Take precautions to keep the water from rising above 60 degrees, or the water lily will break dormancy and be subject to fungal or bacterial infections as the new growth emerges, then decays. Check the water frequently, and replace it often to discourage fungal or bacterial growth.

When your water lilies have lived successfully through the winter, re-pot them and move them outdoors. Tropical water lilies should be placed outdoors well after danger of frost is passed. The water temperature in the pond should be at least 70 degrees. Temperatures lower than 70 will severely stunt, if not kill, most tropical water lilies. Keeping your prized tropical water lilies on your deck in a container water garden for a month or two until the temperature rises may be the best option for you. Heating the container pond is easily accomplished with a good submersible aquarium heater.