Water Cabbage (Pistia Stratiotes) – The Complete Guide

In the finely balanced ecosystem of pond and aquarium, the water cabbage proves to be a valuable component. The tropical floating plant filters the water, provides shady retreats for fish, and decorates the appearance with its gray-green leaf rosettes.

Water cabbage (Pistia stratiotes) is also known by the names water lettuce, shellflower, and Nile cabbage.

Planting Water Cabbage Properly

Do not set out the tropical floating plant until the water in the pond has reached a minimum temperature of 59 °F (15 °C).

If water lettuce is moving from a warm environment to the open water zone, gradually acclimate the plant to cooler water temperatures or do not release it until the water reaches 68°F (20 °C).

Please note that water cabbage and other plants should not cover more than half of the water surface.

Care Tips

Since water cabbage thrives as a floating plant, you will not have to think about complex care.

After all, there are a few precautions to take to ensure that you get a lot of enjoyment from water cabbage:

  • Thin out regularly during the growing season.
  • Remove as many runners as necessary so that a maximum of 30 to 50 percent of the water is covered with plants.
  • In case of deficiencies, fertilize in a separate, waterproof container with a special preparation.

If temperatures fall below 59 °F (15 °C), remove the water lettuce from the pond. The tropical floating plant can overwinter at temperatures between 68 and 77 °F (20 and 25 °C) in a warm water aquarium.

Alternatively, a tub with a clay soil layer and warm freshwater with a pH of 6.5 to 7.2 can act as winter quarters. Since the water cabbage does not go dormant, continue to thin out the plant regularly.

Which Location is Suitable for Water Cabbage?

Water lettuce performs its many tasks as a floating plant with flying colors in a semi-shaded spot in the open water zone of your garden pond.

It will tolerate a sunny location as long as the water cabbage does not come under the blazing midday sun. Please do not expose the plant to currents or the constant water movement near a fountain.

Pruning Water Cabbage Properly

Water cabbage does not need pruning in the true sense of the word. Instead, thin out the vigorous floating plant regularly so that it does not completely annex the pond or aquarium.

The water lettuce tolerates pruning all year round, though. Using a landing net, bring the plant close to you to cut off runners, excess leaves, and stolons with a sharp knife or scissors.

Perform this important maintenance regularly when the plants occupy more than half of the water surface. Further, cut off runners with fully formed adventitious plants if you plan to propagate.

Fertilize Water Cabbage Properly

In a well-balanced pond, adding nutrients is usually not necessary. Only if there are clear signs of deficiency, such as stunted growth or yellow leaves, you should fertilize water lettuce.

Since not all living organisms and plants in the pond react positively to fertilizers, relocate the water cabbage to a separate container for some time.

A layer of soil on the bottom and enough warm freshwater create suitable conditions. Now you can administer a special fertilizer for floating plants according to the manufacturer’s instructions.

Wintering Water Cabbage

Native to the tropics, the water cabbage does not tolerate temperatures below 59 °F (15 °C). Since it nevertheless has a perennial life force, you should take the floating plant out of the water with a landing net in the fall.

In a freshwater aquarium or a separate tub with a clay-covered bottom, overwinter water cabbage like this:

  • Warm water temperatures of 68 to 77 °F (20 to 25 °C).
  • Fresh water with a pH of 6.5 to 7.2.
  • No cover and no heating source nearby.

If no adequate winter quarters are available, get the water lettuce out of the pond anyway. Otherwise, as it rots, all the nutrients stored during the summer will return to the water.

The next year you may then be plagued with a lush algae bloom.

Propagating Water Cabbage

Water cabbage takes care of its own offspring. A vital mother plant produces numerous runners in the form of adventitious plants.

To obtain more specimens for your private water worlds, simply separate the fully formed daughter plants.

Is Water Lettuce Poisonous?

The botanical classification of Pistia stratiotes to the arum family rightly suggests that the plant is not entirely harmless. Since there is a lack of sound scientific knowledge regarding toxicity to date, we recommend cautious handling.

Please do not be tempted by the name water cabbage to consume the green leaves. The substances contained, such as potassium oxalate, cause nausea and vomiting even in small quantities.

Yellow Leaves

Yellow leaves on a water cabbage indicate a lack of nutrients. A pond or aquarium does not always completely cover the needs of this highly consumptive floating plant.

Since adding fertilizer to a garden pond always comes with the risk of an algae bloom, get the suffering plant out of the water with a landing net.

Place the plant in a tub to add a special fertilizer for aquatic plants to the water inside. Once the water lettuce has recovered, you can relocate it to its original location.

How to Care for Water Lettuce in the Aquarium?

In an open warm-water aquarium, water cabbage feels at home under the following conditions:

  • Freshwater with temperatures of 68 to 77 °F (20 to 25 °C).
  • A carbonate hardness of maximum 15 dKH.
  • An ideal pH value of 6.5 to 7.2.
  • A semi-shaded, airy location, away from any source of heat.
  • Thinning out the plant if there is any unwanted spreading.

An aquarium with a cover is unsuitable for water lettuce. The increased heat, as well as dripping condensation under a cover, will significantly affect the vitality and beauty of the water cabbage.

Within a short time, rot will form and the floating plant will die.

Why Does the Water Cabbage Prevent an Algae Bloom?

If crystal clear pond water turns into a yellow-brown broth, it means that algae found enough nutrients for their growth. Thus, there is always a nutrient surplus behind the hated algae bloom.

As a strongly consuming floating plant, water lettuce prevents this deficiency. The long filamentous roots extract phosphorus, nitrogen, nitrate, and excess fish food from the water.

The lurking algae are thus deprived of their basis of existence. Therefore, do not cut off the thread roots, because they contribute significantly to keeping the water in the pond and aquarium clean and free of algae.