Tips for Winterizing Your Water Garden

Help ensure the survival of your plants and fish with a little pre-winter preparation.

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Preparing a water garden before cold weather sets in will help ensure that your plants and fish survive winter. In this project, we prepare two water gardens in Zone 4 for winter weather. Each requires slightly different care. The first water garden features hardy plants and fish. The second pond has non-hardy plants and no fish.

To winterize a pond with hardy plants, fish and a soft liner:

Empty the pond halfway by disconnecting the hose from the pump and reconnecting it to a hose that runs to the ground. Removing this amount of water makes it easier to see and remove the fish during cleaning.

Remove the potted plants from the pond. For most plants, cut back one-third of the foliage. Otherwise, the foliage will die and fall into the water, creating debris which, as it decomposes, produces methane gas. If the water freezes, the gases are trapped and the buildup is unhealthy for fish.

If plants are overgrown, plan to divide and replant them in the spring; repotting in the fall weakens the plant. Cut water lilies back to the base. If the tuber has outgrown its container, remember to divide and replant it next spring. Horsetail doesn't do well when cut back, so just remove dead foliage by gently pulling it from the plant.

Catch fish and place them in a bucket filled with water from the pond. A good way to catch fish is to use two nets and start at one end of the pond, corralling the fish at the other end.

Remove any mulch or debris from the bottom. Debris like leaves or twigs will decompose underwater and create methane gas. The debris makes a great soil amendment, too.

Put the plants back into the pond, placing them at least 1-1/2 feet under the water, below the freezing line. Hardy aquatic plants can stay submerged if the water is at least three feet deep. If you don't have fish, you can allow the pond to freeze — the hardy plants will survive.

Place the pump back into the pond about 1-1/2 feet below the surface of the water to keep the pump from freezing. The pump should circulate only the top one-third to one-fourth of the water in the pond. The deeper portions of the pond where the fish will hibernate should remain undisturbed.

Put the fish back into the pond. Once the temperature drops in late summer or early fall, switch from a high-protein food to one high in carbohydrates. When the water temperature reaches 50 degrees, stop feeding the fish because their metabolism has now slowed. Start feeding the fish again when the water temperature reaches 55 degrees.

Protect fish with an opening in the ice. Use a de-icer, or in warmer climates that may have an occasional freeze, create a hole by setting a pot of hot water on the ice. The heat will melt through and create a hole for the dangerous gases to escape. Never break the surface with a hammer: the shock waves could kill the fish.

To winterize a pond with non-hardy plants, no fish and a pre-formed plastic liner:

Remove leaves and debris from the surface of the pond with a shrub rake.
Remove non-hardy floating annuals and discard. Remove potted tender perennials such as flag iris and narrow-leaf arrowhead, which won't survive icy waters. Store them indoors in a shallow pan of water near a sunny window and they'll be ready to bloom next spring. Remove hardy lilies and the tubers. Rinse them and store them in pond water in a dark, cool — not freezing — location.
Drain the pond. If you have a fountain pump, you can disconnect the fountain attachment and connect tubing to drain the water to a spot elsewhere in the landscape. Be careful to have the pump out of the water only briefly; the motor will burn out if kept out of water too long.