As your water garden plants begin to have more spent leaves than new leaves, it’s time to think about winterizing the garden pond. Water lettuce and water hyacinth aren’t winter hardy in this area and don’t hold over well. As freezing temperatures make these plants unacceptable looking, remove them from your water garden and add them to the compost bin. Non hardy aquatic plants that can be wintered over as house plants should be removed from ponds or tub gardens and brought inside. Hardy plants in pots can usually stay where they have been all summer. Lowering them to the pond bottom isn’t necessary unless winter temperatures cause the pond to freeze below the rim of the pots. Hardy plants most sensitive to freezing are pickerel rush, Thalia, and arrowhead. These can be lowered to the bottom of the pond or covered with deeper water.
Hardy water lilies should be left at their normal pond depth. Remove stems and leaves of plants as they turn yellow. Don’t prune any new foliage growth that is initiated during the winter and stop any fertilization practices during the winter months. Some plants that have interesting foliage can be left un-pruned for dried texture while the pond is dormant.
Here in Central Virginia, fall weather means falling leaves. Keeping the pond clean can be as simple as the occasional removal of leaves from the pond’s surface. Once the leaves sink to the bottom of the water garden, they are more difficult to remove. Lots of decomposing leaves use extra oxygen and can lead to water quality problems if the pond freezes over completely. Some folks opt to cover their pond with netting so that the leaves can’t get in. I prefer to keep things natural so the birds can use the pond during the winter months.
A frozen pond isn’t harmful if the pond is relatively clean before it freezes over. The fish remain dormant below the ice right along with the plants, snails, and frogs. Never break the ice by striking the pond! Hitting the ice can burst or damage the air bladders of the fish causing death. Melt through the ice using hot water poured in a pan placed on the ice if you feel you must have an opening during extended frozen periods. To prevent the pond from freezing over completely, keep the water moving by operating the pump throughout the winter. You can usually run the waterfall during freezing weather, but you should disconnect statuary or fountain nozzles and direct the water flow from the pump straight up toward the surface. If electricity is interrupted during freezing weather, you’ll have to wait until the tubing thaws to turn the system on again. Remove pumps from above ground tub gardens.
Don’t feed fish during the winter or at any time the water temperature is below 40 degrees. Once winter is almost over and water temperatures reach 40-55 degrees, feed with wheat-germ food only. Use regular fish food once the water temperatures climb into the upper 50s.
Garden ponds can be beautiful during the winter months. If you operate the waterfall during the winter, you may see interesting ice formations created where water splashed and builds up. Watch for wildlife, especially birds, enjoying your pond.