Pond plants are not only beautiful to look at but also important for maintaining good water quality in your garden pond. To ensure you continue to enjoy them in the next season, it’s crucial to know how to overwinter them correctly. Native aquatic plants are typically hardy and can remain in your garden pond without any issues. Some plants have their unique ways of dealing with winter by sinking to the bottom and slowing down their metabolic processes. Exotic plants, on the other hand, require a warm spot even during winter and won’t survive the cold temperatures of your local garden pond.
Which plants are hardy for winter?
Native pond plants are hardy and can withstand freezing temperatures, making them well-suited for overwintering in your garden pond. Exotic plants, like water hyacinth, water lettuce, or water cabbage, add visual appeal during the pond season but must be overwintered in a frost-free environment to ensure they thrive in the following season. Several hardy pond plants don’t require any special care as they naturally adapt to the cold. For this to work, your pond should be deep enough. Plants like pondweed and water milfoil anchor themselves to stones or wood at the pond’s bottom and can even survive freezing conditions.
Some water plants form bulbs or rhizomes and can be treated like bulb plants. Plants such as hornwort, water violet, and various water crowfoots retreat completely in late autumn and survive the winter with winter buds. In spring, they reemerge without any special care.
Overwintering native pond and water lilies
Place water lilies in plant baskets or containers within your pond. In preparation for winter, briefly remove them from the pond, cut off dead plant material, and trim them if necessary. Place the plants in the deepwater zone where they’ll be protected from severe winter frosts. Ensure the water lilies are submerged deeply enough to prevent the rootstock from freezing, which would be fatal for the plants.
If you have water or pond lilies in a shallow pre-formed pond or a mini pond, you’ll need to remove them from the water. Place them in a container with water and store them in a frost-free space with diffused light.
Low-maintenance pond plants
Some native pond plants have their strategies for survival and require no special winter care. These plants form winter buds or other dormant stages for the winter. Examples include:
- Water chestnut
- Hornwort
- Water violet
- Water chestnut
- Water weed
- Water horsetail
- Duckweed and frogbit
These plants will come back in spring, growing new shoots without any intervention. Some of these plants are extremely resilient. Remove snow from the ice cover from time to time to allow sunlight to reach your pond.
Trimming fast-growing plants
Plants in the reed zone, such as bulrush, reed, and native rush species, tolerate the winter well. However, they grow vigorously and should be trimmed to prevent their dead leaves from falling into the water and creating unnecessary mud buildup. Trim these plants about 15 centimeters above the water surface to allow for oxygen exchange and to prevent the accumulation of decaying plant material. This also helps to release any trapped noxious gases from the bottom.
For sensitive shoreline plants like pampas grass, bundle them together and protect them from heavy frost using fleece or brushwood covering. In the spring, remove the covering. Plants in ceramic or earthenware containers can survive the winter outside, but it’s a good idea to transfer them to plastic containers and cover them with fleece or brushwood.
Moving shallow-water plants to the deepwater zone
Plants located in the shallow-water zone and the marshy area are often not sufficiently protected during winter and might not tolerate deep freezes. Their ability to withstand cold depends on the specific plant. The warmest area in your pond is the deepwater zone, so some plants must be moved to deeper areas for winter protection. Follow the same procedure as with water lilies: remove the plants from the water in their containers, trim them if necessary, and remove dead parts. Place the plants in the deepwater area, and in the spring, move them back to their original spot.
Keeping evergreen plants ice-free
Some pond plants, like water moss and water starwort, are evergreen. To allow them to perform photosynthesis throughout the winter, you need to keep them ice-free. Move them to areas in your pond that remain ice-free and ensure they receive enough light. When preparing your pond for winter, remove any dead plant material. If your pond doesn’t have a spot that remains ice-free, place these plants in a large container with water and store them in a frost-free, well-lit area.
Overwintering exotic water lilies and lotus flowers
Unlike native water lilies, exotic water lilies and lotus flowers cannot overwinter in your garden pond. These plants often experience a change in their growth cycle between the rainy and dry seasons. To overwinter them, they require water temperatures of at least 10 degrees Celsius. Place these plants in large containers filled with water in a well-lit, frost-free area.
Overwintering exotic water plants
Many exotic water plants don’t have a winter dormant period and cannot withstand the cold in your garden pond. These plants must be brought to a winter shelter in a timely manner. Water hyacinth, shellflower, water poppy, and umbrella plant require plenty of daylight and not just water temperatures above 10 degrees Celsius but also warmer air temperatures. Plants in mini ponds and shallow pre-formed ponds also cannot survive the winter outside and must be placed in winter storage. Ideally, bring these plants to the winter shelter when nighttime temperatures drop below 10 degrees Celsius, preventing them from being exposed to ground frost. Remove frost-sensitive floating plants from the water with a sieve.
Before bringing your plants to their winter shelter, make sure to remove any dead plant material and eliminate any remaining impurities. Replace the planting substrate entirely, using specialized pond soil or granules. Regular potting soil is not suitable. Place the plants in containers with fresh water and replenish the water as needed.
Overwintering exotic floating plants
Exotic floating plants like water lettuce, shellflower, and water hyacinth develop long roots and should, therefore, be overwintered in deep bowls or containers with a water level of at least 15 to 20 centimeters. Add a layer of clay-rich pond soil to the bottom of the container to provide the plants with sufficient nutrients. If you have a warm water aquarium, you can also overwinter floating plants there.
Requirements for the winter shelter
When creating a winter shelter for your plants, try to provide conditions as close to their natural habitat as possible. The temperature should be adequately high, and the plants should receive ample sunlight. Therefore, place them in a well-lit room. A heated greenhouse or a winter garden is an excellent choice. Plants that shed their leaves during the winter can also be overwintered in a dark cellar as long as it’s frost-free or kept at a sufficiently warm temperature. An ideal temperature is around 10 degrees Celsius. Anything higher may cause the plants to sprout prematurely. Some plants, such as water hyacinths, require warmth and should be overwintered at temperatures between 15 and 18 degrees Celsius. When you’re confident that there won’t be any more frost, you can return the plants to your pond.
Conclusion
How you overwinter your pond plants depends on whether they are hardy. Although native pond plants are hardy, they should be moved from the shallow-water zone to the deepwater area. Some plants naturally shed their leaves in winter and don’t require special care. Various pond plants sink to the bottom during cold temperatures. Exotic pond plants are sensitive and must be moved to a winter shelter. They generally need a minimum temperature of 10 degrees Celsius and sufficient light throughout the winter.