Almost alien-looking in their appearance, these velvety green balls might be commonly called moss balls, or Marimo, but they are not actually moss at all. They are actually a growth form of a kind of green algae, which forms into these balls when growing in shallow lakes.
What are Marimo Moss Balls?
Marimo, also known as moss balls, Cladophora balls, or lake balls, is a rare growth form of a species of filamentous green algae called Aegagropila linnaei. The species can be found in the wild in several lakes and rivers of Northern Europe and Japan.
Sadly now rare or in decline in the natural world in many areas, these unusual balls can also be kept as unique houseplants indoors.
The round shape of these balls occurs when wave action occasionally turns them. They prefer habitats in lakes that have moderate to low biological activity and high calcium levels.
Those sold for display in aquariums or other water receptacles usually come from Ukrainian lakes.
If you do decide to grow these at home, please do make sure you know where they come from and make sure they have not contributed to the depletion of wild stocks. The last thing most keen gardeners or houseplant owners will want is to contribute to environmental degradation and species loss in the wild.
Where to Grow Marimo Moss Balls
These are aquatic plants which means, of course, they grow in water. You can place them in any receptacle that you can fill with water and see through to admire the ball-shaped structure within.
Naturally forming on the bottoms of shallow lakes, these plants do not need intense light. Bright but indirect light is just fine for these unfussy aquatic plants.
As long as there is some natural light from a window close by, or you place the container with your Marimo close to a grow light, it should get what it needs for photosynthesis.
It is important to remember that the water in whatever receptacle you have chosen should not get too warm. Remember, when growing this algae indoors, you need to mimic the conditions in the cold northern lakes where it is found.
Make sure the water temperature remains below 25 degrees Celsius and above freezing to avoid encountering any problems.
There are many different containers you might use to fill with water to create a suitable freshwater habitat for these algal balls. You might use a simple glass vase or bowl, even an old cookie jar, or other reclaimed items from elsewhere in your home. You really do not have to rush out to buy anything new.
You might also place this plant in an existing aquarium, as long as it is not kept tropically warm, and as long as the fish inside don’t have a taste for eating algae.
Caring for Marimo Moss Balls
These really are the ultimate low-maintenance plant. Since these are aquatic plants, there will not even be any hassle trying to work out how much to water. Other than making sure that the water is fresh, and moving the balls around to maintain their round form, there is not really much that you have to do.
Maintaining the water for these moss balls simply means making sure that you refresh it every now and then, and that it does not become silted, infested with different algae, or too hot over time.
You simply need to replace the water in your receptacle every couple of weeks or so, and you can just use your regular tap water for the purpose. But if there is chlorine in your tap water, it is best to leave it for 24 hrs before you use it or to use a de-chlorinator.
Moving Moss Balls to Maintain their Shape
In a natural lake environment, the balls form into spherical globes because they are moved by the waves or water movement. Of course, when you have them in a glass vase or aquarium there will not be natural waves. So you will need to turn your moss balls regularly so they do not lose their shape.
If your moss ball does become misshapen, don’t worry. You can simply roll it back into shape again between your palms. Likewise, if it splits apart, you can simply roll the pieces back together.
These are hassle-free plants on the whole. But certain issues can arise if the environmental conditions are not quite right. Fortunately, any problems are usually easily rectified by amending the environmental conditions that were not quite as they should have been.
If a marimo moss ball turns brown, for example, it might be getting too little light, or the temperature of the water may be too high.
If a marimo moss ball turns white, it may have had too much light. Slimy white stuff might be competing algae that should be removed to prevent issues.
If a marimo moss ball has black parts, this is rot (usually caused by adverse conditions over longer periods). But all is not lost. You can remove any dead black parts, solve any environmental issues, then roll what remains into a new ball. It should recover.
Propagation is also very easy, so once you have a moss ball that is thriving, you can easily get more.
Though the balls only grow slowly, small pieces will eventually shed off the ‘mother’ ball without you having to do anything at all. Roll these new bits regularly and they will become new balls over time.
You can also simply take an existing ball and break it apart yourself to make new mini-balls. The sections will be rather irregular at first, but roll them regularly and you will have several new balls to look at.