Aquatic Gardens Still Need Care In Fall, Winter

Daniel Gill, Merrill, Thomas A.  |  10/28/2005 2:35:49 AM


Get It Growing News For 11/18/05

By Dan Gill
LSU AgCenter Horticulturist

Few gardeners can resist the visual beauty and delightful sound that water brings to the landscape, and as a result aquatic gardens have become quite popular with Louisiana gardeners.

Chilly weather and light freezes already have encouraged dormancy in some aquatic plants and the growing season for aquatic gardens is winding down, but those gardens still will need some of your attention in late fall and winter.

As we move into the winter, here is some information on what you need to do.

As long as the weather is mild and the water temperature is above 40 degrees, you can continue to run the pump. When the weather is nice and you are working in the yard or sitting on the patio, the delightful sound of water can be just as welcome in winter as it was during the summer. Just be sure to unplug the pump during periods of sub-freezing temperatures.

Lots of shade trees drop leaves this time of year, and it can get to be a real hassle keeping them cleaned out of the pond. It is important, however, to skim the pond regularly to remove these fallen leaves. If allowed to stay on the water, the leaves eventually will sink to the bottom of the aquatic garden and decay. Decaying leaves foul the water and can cause a variety of problems.

Place netting over the pond to catch the leaves if the pond is not too large to easily skim. It is far easier to occasionally dump the leaves off the netting than to skim them off the pond. Put the leaves in your compost pile. Make sure the edges of the netting are staked down to keep it from blowing off of the pond. Then, when the trees have dropped most of their leaves, the covering can be removed.

This time of year you will notice that your water lily plants have grown smaller and stopped blooming. Most tropical water lilies would bloom year-round except that winter temperatures are too cold and the days too short. Tropical water lilies are not reliably hardy here, but some gardeners grow tropical water lilies as annuals and let them take their chances in the pond over the winter. If you want to hedge your bets, bring pots of tropical water lilies inside and submerge them in buckets of water, or store the roots and crowns in wet sand in an area that will stay between 50 and 60 degrees. They will be dormant and have little or no foliage, so light does not need to be provided to them. On the other hand, hardy water lilies do not need to be brought in. Just set the pots on the bottom of the pond.

Most of the marginal and bog plants in your aquatic garden are hardy. Do not be confused when these aquatic plants turn brown and go dormant. They are not dead. Cut them back hard and set the pots deeper in the water – below the level where the water may freeze (on the bottom of the pond if it’s not too deep). As long as the crowns and roots stay below any ice that forms, they will be fine. Ice occurs occasionally, if at all, around here, and it rarely gets more that an inch or two thick.

Promptly cut back and remove any dead or damaged foliage from aquatic plants whenever it occurs during the winter. Aquatic gardens and ponds don’t look their best in the winter, but we can at least keep things looking neat. Also, allowing dead leaves and stems to accumulate in the water may cause problems and will make it more likely that you’ll have to do a major cleaning in spring.

Louisiana irises are in active growth during the wintertime. If you included them in your aquatic garden you will have at least some green.

Water hyacinths and water lettuce are commonly grown floating water plants that are not reliably hardy during the winter. If temperatures will get into the mid- to low 20s, bring a few plants inside and keep them in a plastic bag or float them in a large container of water. If the freeze gets the ones in the pond, at least you will have saved a few (and a few are enough). Place them back into the pond after the cold weather passes and repeat as necessary. Both of these plants can become major pests in lakes, ponds and waterways, particularly in South Louisiana, so you should never introduce these plants into natural bodies of water.

There is no need to move your goldfish or koi inside for the winter, and you do not need to put a heater in the pond. These fish go into a natural semi-hibernation when water temperatures fall below 45 degrees. Koi and goldfish do not need to be fed when temperatures are that low, and they should be fed sparingly over the winter if at all. Should the pond freeze over, the fish will be fine in the liquid water underneath the ice.

Though ice rarely lasts more than a few days, there should be some openings of liquid water in the ice to allow the oxygen exchange needed by the fish. If you need to create openings, be sure not to strike the ice to break it, because you might hurt the fish. Instead, pour a little boiling water on the ice to open a hole. Another idea is to place one or two milk jugs about one-quarter full of water in the pond before the ice forms. Remove them once the ice layer has formed to create holes.

Aquatic gardens don’t require as much work to care for them during the winter, but it is important to keep an eye on things. Efforts made over the next few months can make spring cleanup less of a hassle and ensure the beauty of your garden next summer.

Get It Growing is a weekly feature on home lawn and garden topics prepared by experts in the LSU AgCenter. For more information on such topics, contact your parish LSU AgCenter Extension office or visit our Web site at A wide range of publications and a variety of other resources are available.


Contact: Dan Gill at (225) 578-2222 or
Editor: Tom Merrill at (225) 578-2263 or

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