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Garden Variety: Winterizing water features

By Jennifer Smith

Gardeners with landscape ponds and other water features have a little work to do with the arrival of freezing temperatures. Whether pumps and filters are left up and running or turned off for winter, mid- to late-November is the time to winterize water features in the Lawrence area.

Cleaning is the most important part of winterizing. Debris from water garden plants, falling leaves and other plant materials breaks down and accumulates in the pond through the summer and fall. The materials deplete the water of oxygen as they break down and accumulate in filters. This is a good time to shut everything down, disconnect pumps and filters, and blow air through all plumbing lines. Hook everything back up and restart it if the pump/pond will be left on through the winter, or store the materials until the pond is ready to get going again in spring.

For pumps and filters that are left running during winter, consult a water garden specialist or the product manual for specific information. For ponds that are shut down over winter, remove water until it is below the perimeter stonework to prevent damage from freezing and thawing. Gardeners can also consider shutting pumps down but using a winter bubbler, a small air pump, or a floating de-icer to keep part of the pond open in freezing temperatures.

If the water feature has fish and plants, they also need attention.

Hardy fish such as comet goldfish and koi are fine left in the water if the pond is at least 24 inches deep. Their metabolism slows with cooler temperatures, so the general rule is to stop feeding fish when water temperatures are below 50 degrees. They will survive on material in the pond over the winter. Move tropical fish species or fish from shallow ponds to indoor aquariums.

Plant care depends on the plant type. Hardy and marginal plants including lotus, sedges, rushes and some lilies stay in the pond, but remove dead foliage and drop them into the deepest water. Tropical water lilies and other tropical water garden plants must be overwintered inside or removed and discarded from the pond in the fall.

Discarded plants should be composted on site or placed in the trash rather than dumped in another waterway because of the chance of them being carried downstream and becoming problems elsewhere.

Nets (hopefully already in place) help to keep falling leaves and other plant debris out of water features. Remove nets when most of the leaves have fallen, usually the first part of December.

If water features are near trees that hold their leaves through all or part of the winter, leave nets in place as long as necessary.

— Jennifer Smith is a former horticulture extension agent for K-State Research and Extension and horticulturist for Lawrence Parks and Recreation. She is the host of “The Garden Show” and has been a gardener since childhood. Send your gardening questions and feedback to features@ljworld.com.