Many gardeners are enjoying a renewed interest in water gardening. Water adds a special effect to the landscape and fish are easy to care for pets. A properly functioning water garden takes care of itself naturally throughout the growing season. Submerged plants and scavengers help keep algae populations from getting out of hand. However, water gardens do require late season attention for their survival.
Keep falling leaves and twigs out of the pond to prevent injury to the fish. Prevention is also easier than having to clean the entire pool in the fall. Netting stretched across the pool is an easy preventative to catch leaves or use a skimmer to remove leaves on a regular basis.
If your pond contains fish, be sure to feed them extra food beginning when temperatures cool and continue until the water temperature drops below 45 F. This allows the fish to build up additional fat stores for winter survival. If the fish are to remain in the pond throughout the winter, it is necessary to keep an area free of ice throughout the winter. This allows the exchange of gases such as carbon dioxide, methane, and hydrogen sulfide which are produced from decaying organic matter. The build up of these gases is toxic to fish. A one foot diameter opening per 100 square foot of pond surface area is adequate.
Stop fertilizing water garden plants when the daytime water temperature drops below 60 F. This will give plants the opportunity to go dormant. As the leaves of hardy plants yellow or are frozen, cut the leaves off back to the crown. The short, small leaves produced late in the season should remain attached. Lower hardy plants to the bottom of the pool where they will survive the winter. If there is danger of the pool freezing solid, remove the plants in their containers from the pond and place them in a non-freezing area. Put the containers inside a plastic bag and cover with moist material such as newspapers or peat moss to retain moisture.
Tropical water lilies and other non-hardy water plants can be over-wintered in various ways. The goal is to keep the plant alive, but not growing vigorously. Plants can be kept in a washtub, tank or even in an aquarium in a greenhouse or under artificial lights. Light the plants for 12 to 18 hours. The water temperature should be maintained around 70 F. Plants which form tubers such as tropical water lilies can also be stored as a dormant tuber. The plants should not be fertilized after August. This forces the lily to form a tuber. Allow the plant to remain in the pond until all leaves are killed by frost. A hard tuber must be present in order for the plant to survive. Once tuber formation is complete, remove it from the container and wash it off. If the tuber has roots or stem tissue attached, let it air dry for a few days and then break the roots and stems off. Place the tuber in a jar filled with distilled water and store it in a cool (55 F), dark location. Check the container regularly and replace the water if it is discolored. In the spring, place the container in a sunny warm location. When sprouts form, plant the tuber in sand. Place the planted tuber in a container of water so that developing leaves can float. When the leaves have grown to the water's surface and white feeder roots can be seen, remove the plant from the tuber and plant it into a standard container. Place the lily in the outdoor pond when the minimum water temperature is 70 F or more.
If the pond has an inch or more accumulation of silt, leaves or debris, the pond requires cleaning. Place some of the original pond water into a holding tank for the fish. Cover it so fish don't jump out. Remove the remaining water from the pond. Remove and cover plants with wet newspaper or other moist material and place the plants in a shady location. After all the water is removed, scrub the pool floor with a stiff brush and water. Leave the algae growing on the side of pool. Rinse the pool and drain once again. Fill the pool with fresh water and allow the chlorine to evaporate and water temperature to stabilize. Blend the new pond water with water in the holding tank until its water temperature is within 3 F. of the pond water. Release your fish and scavengers into the pool. Divide and repot those plants that need it and put them back in the pool or store them in a frost free area for winter.
Water gardens are a beautiful addition to the home landscape. However, they are not a low maintenance addition. For a lower maintenance water garden, select only hardy species and install a pond that is deep enough for overwintering plant material. Installing a water heater is also an excellent alternative.
This article originally appeared in the October 14, 1994 issue, p. 147.