Q. Next year I will be installing an above ground pond with a capacity of about 500 gallons. The winters are severe where I live, so the pond will need to be emptied in the fall. What concerns me is what to do with the water plants during the winter. I cannot find any information on what to do with them so I can use them again in the spring. I’m hoping you have suggestions. Otherwise, I’ll have to buy new plants each year.
A. Many aquatic plants can be overwintered outside the pond. The trick is to make them go into an ordinary winter “sleep mode.”
Wait until the shortening days and cool weather of the fall cause growth to stop and leaves to begin to die back. Trim off the remaining leaves. For lilies and lotus I suggest trimming to within an inch or two of the tuber. For iris, pickerelweed and other emergents, trim to leave about 6 inches of the stalk. Submergents should not be trimmed at all.
You will need a cool (45 to 50 degrees Fahrenheit), dark location to store the plants. One storage method is to unpot the plants, wrap them in damp newspaper and bag them in sealed plastic bags. Check the plants every week or so to maintain moist conditions. Only floating leaf plants and emergents can be kept in wet newspaper.
Another method is to settle them in water-filled tubs. Floating leaf plants and emergents should be left in their pots, and the pots should be placed in water just deep enough to cover the roots, tubers and so on. Submergent plants (if grown in pots) should be placed in tubs deep enough to cover the plants. If the submergents are unpotted they can just be placed in water.
There are two possible risks. First, watch for fungus or rot. Good air circulation around the plants will limit this problem, which is why I prefer the second method I described above.
The other danger is animals. Mice like to chew on plant tubers for winter food. Make sure the plant material is protected from hungry pests.