How do you overwinter water lilies

In many gardens, the garden pond is an important design element, which, however, only unfolds its effect with the right planting. A large number of aquatic and marsh plants are commercially available, but not all of them survive the cold season without damage. Whether water lilies and other plants are actually hardy depends not only on their origin, but also on the depth of the water.

The deeper the garden pond, the easier it is to overwinter

A naturally designed garden pond consists of three different zones that are filled with different types of pond plants and are also treated differently during the winter months. Basically, the following rule applies: the deeper the garden pond or a certain area, the easier it is to overwinter. Waters more than 160 centimeters deep rarely or never freeze to the bottom, instead, even with outside temperatures of more than minus ten degrees Celsius, plus degrees prevail here. For this reason, fish, but also many floating plants, hibernate here more easily. Plants from the swamp or shallow water zone, on the other hand, have to be specially protected during the winter months, depending on the species and variety.

Tip: Some plants in the shallow water zone, such as native species of water lily, can be moved to the deep water zone before winter sets in and survive the cold season there more easily than in shallow water. For this it is practical not to plant the plants directly in the pond floor, but instead in mesh baskets. So they can be easily lifted out and moved in autumn.

How to overwinter aquatic plants from mini ponds

Conversely, of course, the lower the water level, the more dangerous it is for the aquatic plants. Mini garden ponds, which are sometimes set up and planted in pots and planters such as a zinc tub, freeze to the ground very quickly in frosty conditions. As a result, even those aquatic plants die which, as native species, are used to frost. However, it is problematic if the rhizomes of the water lilies also freeze through and can no longer supply the plant with moisture and nutrients. Therefore, the following applies to mini ponds: Always overwinter them frost-free, but cool at temperatures of less than ten degrees Celsius. If the container is too big and / or too heavy, you can also drain the water down to a few centimeters or put the plants and their baskets individually in buckets or larger planters over the winter.

Tip: When wintering indoors or in a greenhouse, you should always keep in mind that the darker it is, the cooler the ambient temperature must be. If the plants overwinter too warm, their metabolism is stimulated and they quickly suffer from the lack of light. In a rather dark winter, the temperature should be just above zero.

Not all water lilies are hardy

There are around 50 different types of water lilies worldwide, many of which are native to our latitudes. Others come from the tropics and would not survive a cold winter outside in the garden pond. It is best to overwinter native and therefore hardy water lilies as follows:
  • Lowering to a water depth of at least 60 centimeters
  • some species also at a depth of one to one and a half meters
  • Removal of dead and rotten plant parts in autumn
If a hardy water lily is in a very small pond less than 60 centimeters deep, you should either move it to a deeper pond or overwinter it in the house in a frost-free and cool place. Even with the hardy species, the rhizomes must not freeze through, otherwise the water lily will no longer sprout so magnificently in the following year.

Tip: When buying hardy water lilies, pay attention to their origin: Some actually native species are imported from aquatic plant schools in Asia, where they of course cannot be hardened accordingly - and do not develop the desired winter hardiness despite their predisposition.

This is how hardy pond plants overwinter

Many other typical pond plants are also native to us and have developed their own individual tactics for wintering. Some - for example reeds - are extremely frost-resistant from the start and do not require any special pruning, they should only be cut back in the spring before budding. Others, on the other hand, such as crab claws, sink to the bottom of the pond in late autumn, hibernate there and reappear on their own in spring. In order for these species to survive the winter, however, the pond should be deeper than 60 centimeters. Many pond plants form so-called winter buds in autumn, from which they finally sprout again in spring. For this reason, these species, including the waterweed, may no longer be pruned from August - with a late pruning, you would remove the winter buds and thus prevent them from sprouting again.

Prepare your garden pond for winter

So that your hardy pond plants survive the cold season as well as possible, you should not only winterize the plants, but also the entire garden pond in autumn. This includes the following work:
  • Let the water pump run empty and overwinter frost-free
  • Remove all leaves from the surface of the water
  • Remove sick and rotten parts of the plant with pond scissors
  • remove these from the pond as well
  • Thinning out too dense stands of plants
  • Thin out the reeds
  • Remove digested sludge with a pond sludge vacuum or a bucket
  • If necessary, use an ice preventer
Tip: Digested sludge forms from the dead plant parts that have sunk to the bottom of the pond. It releases poisonous hydrogen sulfide gas, which can be dangerous for fish and plants, especially under an ice cover. However, digested sludge makes a very good fertilizer and can also be disposed of on the compost.

Hibernate sensitive pond plants properly

Not hardy, tropical pond plants should be moved into the house before the first frost. Like water lilies that are not hardy, they overwinter, frost-free but cool at a maximum of 10 ° C. These species are only allowed to go outside after the ice saints in May, but then have to be slowly accustomed to the sun again. In addition, many plants from the swamp zone are only partially hardy. They can stay outside, but should be moved into deeper water. Here they can withstand temperatures of minus 10 degrees Celsius and more without any problems.

Tip: Pond plants overwintered in the house or greenhouse must be checked regularly. If necessary, you should check the water level, because the plants must not dry out under any circumstances. Wintering in a dark cellar is not recommended.