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Winter Cattails

How To Overwinter Your Water Garden Plants & Fish

How To Overwinter Your Water Garden Plants & Fish


  • Treat Water Hyacinths and Water Lettuce as annuals and replace them every year.
  • Remove them completely when frost hits and compost them.

Tropical Marginals

  • Tropical Marginals cannot survive freezing. They should be treated like annuals and replaced each spring or you can try to overwinter them indoors. In order to do this, they must be removed prior to a killing frost
  • Umbrella Palm, Papyrus, and Parrot Feather can be grown as houseplants. Simply position them in a sunny window and keep moist. It isn’t necessary to keep them in standing water. When the pond water temperature reaches 21°C (70°F) in spring they can be returned to their shallow position in the water garden.
  • For Canna and Taro, remove the plants from the pond and let them dry out naturally. When the foliage has died back, cut it off just above the bulb or rhizome. You can keep it in its original pot but don’t let the soil dry out. Another option is to remove the bulb/rhizome, rinse off any soil that clings to it, and store it in slightly damp peat moss or sand, or place the pot(s) in a tub of water in a cool basement that’s 4-13°C (40-55°F).


Water Lettuce

Water Lettuce

Tropical Water Lilies

Tropical Water Lilies can be replaced each year or overwintered indoors. If you choose to over-winter them there are 2 methods.

Keep them actively growing by placing them in warm water with bright light and warmth. It will be difficult to maintain a minimum water temperature of 21°C (70°F). This may only be possible in a greenhouse or sunroom. If your Lily survives it can be returned to the pond when the water temperature reaches 21 °C (70°F), which is usually in early June.

 Over-winter a tropical Lily by letting the tuber go dormant.

  1. Leave the plant in the pond until after a killing frost. The cold water will induce the formation of a small, black, grape-size tuber. Older specimens may have already produced several.
  2. Gently rinse all the soil from the tubers and float them in lukewarm water for a day. Viable tubers will sink and spoiled ones will float. Discard the spoiled ones. Place the viable tubers in damp peat moss or sand and store in a cool basement. Check them from time to time to make sure the peat moss or sand doesn’t dry out completely.
  3. In early May check to see if the tubers have any sprouts. If there aren’t, place the tubers in distilled water in a sunny window to break dormancy. When roots are 1-2.5 cm (1/2″ – 1″) long pot them 6 mm (1/4″) deep in heavy soil and submerge the pot(s) in 7 cm (3″) of water. Maintain a minimum water temperature indoors of 21 °C (70°F). When leaves emerge and the pond is at least 21°C (70°F) they can be safely returned outdoors to the water garden.

Hardy Marginals & Bog Plants

This group of aquatics can be left in the pond over the winter if it’s at least 50 cm (18″) deep.

  • After frost has killed the foliage, remove the leaves and move the plants to the deepest part of the pond.
  • Don’t cut back the stems of Cattails, Rushes, Reeds, or other plants with hollow stems. If these stems fill up with water the crown of the plant can rot.
  • For shallow pools or streams, plants would need to come indoors and be placed in a tub of water in a cool place like the basement. The temperature should be around 4-13°C (40-55°F).

Water Lily

Hardy Water Lilies & Lotus

  • Hardy Water Lilies and Lotus can be left in ponds as long as the roots and crown do not freeze solid and if they can be moved to a depth of at least 80-90 cm (2 1/2-3′).
  • Later in the fall, remove all foliage so the leaves don’t decompose in the water.
  • If the pond is shallow and likely to freeze, remove old leaves and bring the plants indoors. Place in a tub of water, and store in a cool, dark place.
  • Return plants to their proper depth after the ice has melted the following spring. Or, remove the Lily from the pot, cut off all foliage, and rinse all the soil off the rhizome.
  • Store the rhizome in damp peat moss or sand in a plastic bag at a temperature of 4-13°C (40-55°F).
  • Keep the peat moss or sand moist all winter. If the storage medium is too wet, the rhizome will rot. If too dry, the rhizome dehydrates and dies.
  • Re-pot the tubers in spring and return to the water garden after the ice melts.

Fish, Frogs & Snails

Fish can be left in a pond if it’s at least 50 cm (30″) deep in one area.

  • Stop feeding them when water temperature drops to 10-13°C (50-55°F).
  • Keep an area heater or bubbler going so toxic gases that collect under the ice can escape. You could also bring fish indoors before the water temperature drops to 10°C (50°F) and place them in an aquarium or tank. Keep the water relatively cool and feed moderately. Filtration and oxygenation is needed.
  • In spring, return the fish to the pond. Minimize stress by avoiding a sudden temperature change. (No more than 10°C) Carry your fish out in a bucket and slowly add water from the pond to the bucket at 10- to 15-minute intervals. Use a pond thermometer to check the water temperature as you go.
  • Tadpoles, frogs, and snails need somewhere to bury. If you aren’t overwintering hardy plants in the pond, place a pan of sand in the bottom into which they can burrow and hibernate until spring.