Winter Care of Water Gardens

How to Winterize a Water Feature

preparing a water garden for winter

 The Spruce

Some winter care is necessary for most water gardens and water features, in cold climates. What you need to do depends on how cold it gets in your area and what type of water garden you have. Small container water gardens should always be drained and stored. Natural water gardens and ponds can be left to face the elements. But man-made water gardens will need some extra care and protection.

When Should You Start?

Most winter care starts about the same time frost hits your area. Some of your plants will succumb to the cold and others will slowly be going dormant.

What to Do

For Plants:

  • Stop feeding your water plants in mid-September.
  • Decide which plants you want to over-winter and which can be replaced in the spring. Small floating plants can be difficult to keep indoors all winter and are not as expensive to replace as larger, ornamental plants.
  • Remove any plants that are not hardy. You don't want them decaying in the water. If you wish, you can bring many indoors, to over-winter in a plastic tub filled with water.
  • Hardy plants should be moved to the deepest part of your water garden, for added protection. Remove any dead foliage and flowers and trim them back to a few inches above the soil line, before you move them. They could also be brought indoors, as houseplants, if you have the room. [Don't totally submerge cattails.]
  • Hardy water lilies can be left in the garden, but tropical water lilies should be lifted and brought indoors. They can be stored bare root, in a method similar to non-hardy tubers. How to over-winter waterlilies
  • When discarding plants, floaters can be tossed onto the compost heap, but use discretion with any plants that spread rapidly, like water pennywort (Hydrocotyle), which could potentially over-winter in the compost and become a nuisance.

A chart of water plant hardiness is at the end of this article.

For Fish: (Goldfish and Koi) Cold water will slow the metabolism of fish and they won't need to be feed very often. It is also advised that you switch to a low protein food, to avoid excessive levels of ammonia in the water. Once the water temperature slips into the low 60s F., start feeding with a food labeled low-protein or spring/autumn food and don't give them more than they consume immediately. You can stop feeding entirely when the fish no longer come to the surface of the water asking for food.

For the Water Garden Itself: Hopefully your pond is in good, clean shape prior to winter. If not, clean-up will take a little more effort. For all ponds:

  • Remove all dead plant material. This should be done throughout the year. To keep fall leaves from filling the garden, drape a fine net over the garden, before the leaves start to fall. I raise mine a little, with an arched PVC pipes, so that wildlife, like frogs and birds, do not get trapped underneath. You can then lift the net and most of the leaves. Clean the remainder with a long handled net or skimmer.
  • If there is an excessive amount of debris on the bottom of your garden, you can try using a vacuum, but you may need to drain and clean it. Before you do, test the water pH and temperature. Move any plants and fish to a temporary holding bin. Drain and clean the pond. This is also a good time to check if any repairs are needed to the lining. Then refill with water and wait until the temperature and pH have adjusted back to pre-cleaning numbers, before returning the fish and plants to the pond. [If the water you are refilling with is chlorinated, you will also need to use a dechlorinator.] The plants can go back into the deepest section of the pond. Reintroduce the fish slowly as you would with any new fish.
  • If you are in an area where the water in your water garden will freeze, you will need to prevent the entire surface from freezing solid. Plants and fish need oxygen, even during the winter. You have several options for keeping an opening in the ice.If you only occasionally get hard freezes, you can keep the pump running or use a bubbler.
    Areas with hard winters should not keep their pumps running, because the tubing can freeze and burn out the motor and it can also crack, particularly if there is repetitive freezing and thawing, expanding and contracting. (Now is a good time to clean the pump and filters.) In lieu of the pump, you will need to use some type of floating de-icer. There are electric, battery powdered and solar options available, but make sure there is enough regular sunlight, before trusting to a solar de-icer. An aerator is also advisable, if you have fish. [If you have a waterfall flowing into your water garden, you may be able to keep everything running all winter, depending on where you garden and the power of your pump. Consult your pump manufacturer or the company that installed your water garden.]
  • Monitor the water level, throughout the winter. If the level drops by several inches, you will need to top it off, to protect the submerged plants and fish.

Hardiness of Common Water Plants

Water Plant Hardiness
Arrowhead (Sagittaria) 5 – 11
Arum (Calla) 4 – 8
Cardinal Flower (Lobelia) 3 – 9
Cattail (Typha) 2 – 11
Floating Heart (Nymphoides) 6 – 11
Frogbit (Hydrocharis) 6 – 11
Iris (Iris) 3 – 9
Parrotfeather (Myriophyllum) 5 – 11
Rush (Juncus) 4 – 9
Rush (Scirpus) 3 – 9
Sedges (Carex) 3 – 9
Sweet Flag (Acorus) 4 – 11
Taro 9 – 11
Water Celery / Parsley (Oenanthe) 5 – 11
Water Clover (Marsilea) 6 – 11
Water Hibiscus (Hibiscus) 5 – 11
Water Hyacinth (Eichhornia) 8 – 11
Water Lettuce (Pistia) 9 – 11
Water Lily - Hardy (Nuphar) Varies
Water Lily - Tropical (Nymphaea) 10 – 11
Water lotus – Hardy (Nelumbo) 4 – 11
Water Poppy (Hydrocleys nymphoides) 9 – 11