In March of 2024 I purchased 5 adorable Marimo “moss” balls because I was looking for a unique, low-light level plant that I could display in my bedroom. I love keeping house plants, but the one small window that exists in my bedroom is partly blocked by my vanity mirror. I really wanted to find a plant I could keep without having to set up plant lights.
Enter my Marimo. After a long (6 month!) quarantine period, I set them up in a glass jar in my bedroom. Although Marimo are often referred to as ‘moss balls’, they are actually a type of algae. They are native to cold water lakes in Japan and Iceland and, in their ball form, are typically found rolling around on lake beds where not a ton of sun reaches. This makes them ideal for survival in low light conditions, like in my bedroom!
An Update on My Marimo Balls
As much as I love plants, I have to admit that I don’t have the greenest of thumbs. I feel like it’s always a bit hit or miss whether I end up keeping a plant alive or not. That makes me especially happy to report that, after just over two years of having them, all 5 of my original Marimo balls are still alive and well!
Marimo balls are thought to be able to live over 200 years in their native Japan! I’d feel pretty bad if I somehow managed to kill mine off in just 2 years.
That’s them, in their set up, in the photo near the top of this post. I have to admit that I really barely do anything to care for my Marimo. I think I changed their water just a hand full of times in the past two years. I make sure to open the curtains for them every now and then, so they can get some light, and keep an old chopstick next to their jar so I can stir them up every now and then. The balls moving around in the water helps them to maintain their shape.
How Quickly Do Marimo Balls Grow?
You may have noticed that…well, my Marimo balls are still so small that you can barely see them in the photo above. Wait! Before you blame me… it’s actually normal for Marimo balls to grow very slowly!
Marimo balls typically only grow about 5mm, or 0.2 inches, per year.
In fact, your “Marimo” ball growing too quickly can actually be a sign that you were sold another type of algae, or moss, incorrectly being marketed as a Marimo. Wild Marimo balls live in cold, slow moving, nutrient poor waters, factors that don’t exactly encourage fast growth.
I thought it might be interesting to compare photos of my Marimo balls from two years ago verses photos of them now! I didn’t actually think to measure them when I first got them. But what I did do was take a photo of them with these silly, overpriced, Marimo marbles that I got.
Here’s a photo of my Marimo balls from 2024…
And here they are now, in April of 2026…
They…uhh…look the same size? Maybe a tiny bit bigger? What do you think?
See Ya Next Year!
I have to admit I don’t mind that Marimo balls grow so slowly. They’re so low maintenance that you just have to forgive them for growing slowly. And they’re such a unique, interesting ‘plant’ that you can hardly call them boring, despite them looking essentially the same for years.
I think it’ll be really cool someday, gods permitting when I’m a super old lady, to look back at my Marimo balls and remember how small they were when I first got them! Although writing this post made me realize I’m probably going to be leaving these things to someone in my will.
If you found my site while researching how to care for Marimo balls, you can check out all the other posts I’ve written about them here. I’ll try to post another update about my little Marimo buddies again sometime, although, considering how slow they grow, don’t expect it to be anytime too soon!
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