How can I get rid of mold on my bonsai?

April 27, 2012 6:16 AM

What can I do about mold on the soil of my plum bonsai? Do I need to worry about it?

I bought a plum bonsai from the local grocery store a little over a month ago. It bloomed just fine and grew leaves; about half of them turned yellow and fell off, but the ones left look green and healthy and there's a lot of them. However, since around the time it grew leaves, the surface of the soil will grow a layer of soft, gray fuzz. If I churn the surface soil a bit it breaks up the mold very easily, but it grows back in a few days.

I water the plant maybe twice a week and I put it in a room with a large, sunny North-facing window with beveled glass. I've never had plants until recently, so I'm not really sure what to do with this. I live in Tokyo.

posted by 23 to home & garden (4 answers total)

With the yellowing and falling off of leaves and the soft gray fuzz (which is most likely fungus and not mold), it sounds like over-watering. When and how often to water depends on a lot of factors, like the soil, the size of the pot, and so on, so it'd be hard to give you exact advice on when to water. With that said, the soil does need to dry out a bit between waterings. I usually stick a finger in the soil and water when it feels dry down to about a centimeter.

Maybe this page will give you some ideas on how to know when to water.
posted by Orb at 6:48 AM on April 27, 2012

Sounds like the roots and such are rotting underneath the moss. Is it moss covering? You should take the tree out of the pot, clean it, rinse out the roots, cut off anything that is rotting and repot it with new soil. I think either the potting medium is holding the moisture so the watering is too much or the potting medium needs to be changed. Try repotting and then see what happens. The leaves usually turn yellow and fall off when there is too much water and a fungus is present. You can use some dish detergent to wash the roots and the pot out too. It won't harm the plant.
posted by Yellow at 6:51 AM on April 27, 2012

Thanks for the watering guide! I never would have connected yellowing leaves with overwatering.

I'll repot it and see how it goes. Thanks!
posted by 23 at 1:54 AM on April 28, 2012

Laid off the water and the mold disappeared. Checked the roots and, thankfully, there were fine. Thanks for the advice!
posted by 23 at 12:14 AM on May 28, 2012