As long as the submerged plants are below the ice, they will usually survive the winter in most zones. Any part of the plant that is allowed to freeze will turn to mush and add unwanted debris to the pond. It is wise to cut these plants back.
Anacharis (Elodea canadensis) is a submerged plant or oxygenator. All ponds should have submerged plants to aid in maintaining clean and pure water. They help prevent algae growth. Anacharis grows in sun and shade and can be in water 1-10 feet deep. Each pond plant only spreads to about 12 inches. Anacharis will often overwinter outdoors in your pond successfully in zone 5 and above. You would need to cut it back to below the freeze line. It is a good underwater plant for removing phosphates from your pond water. The submerged plants can be potted in one gallon containers with pea gravel to hold them in place or they can be weighted and dropped to the bottom of your water garden. Completely submerged these plants to a depth of at least 12 inches.
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