Take care of aquatic gardens in fall and winter

Richard Bogren, Young, John, Gill, Daniel J., Owings, Allen D.

News Release Distributed 11/20/09

By LSU AgCenter Horticulturists Dan Gill, Allen Owings and John Young

Including a water feature in the landscape provides an oasis for a wide variety of wildlife. Providing habitat for wildlife is a principle of sustainable landscaping, and as a result aquatic gardens have become quite popular with Louisiana gardeners. Chilly weather and light freezes in late November encourage dormancy in most aquatic plants, and the growing season for aquatic gardens is winding down. As we move into the winter, aquatic garden care changes.

As long as the weather is mild and the water temperature is above 40 degrees, you can continue to run the pump. Unplug the pump during periods of sub-freezing temperatures.

Lots of shade trees drop leaves now, and it can 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 (they make a great addition to the compost pile). If allowed to stay on the water, they will eventually sink to the bottom of the aquatic garden and foul the water.

If the pond is not too large, place netting over it to catch the leaves. It is far easier to occasionally dump the leaves off of the netting than to skim them off of the pond. After the trees have dropped most of their leaves, the covering can be removed.

You will notice your water lily plants have grown smaller and even stopped blooming. 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. Hardy water lilies fit in better with a sustainable landscape and do not need to be brought in. 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, and rarely gets more that an inch thick.

Promptly cut back and remove any dead or damaged foliage from aquatic plants during the winter. Aquatic gardens and ponds don’t look their best in winter, but we can at least keep things looking neat. Louisiana irises are in active growth during the wintertime. If you included them in your aquatic garden, you will have at least some green.

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 should be fed sparingly over 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. Do not strike the ice to break it because you may hurt the fish. Instead, pour 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 ice forms. Remove them once the ice layer has formed to create holes.

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

Visit LaHouse in Baton Rouge to see sustainable landscape practices in action. The home and landscape resource center is located near the intersection of Burbank Drive and Nicholson Drive (Louisiana Highway 30) in Baton Rouge across the street from the LSU baseball stadium. For more information, go to www.louisianahouse.org and www.lsuagcenter.com/lyn.

Rick Bogren

11/20/2009 8:39:31 PM
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