How can I stop mold from growing on the surface of the soil around my potted plants?

Question

I've been growing some apples from seed. I had four growing in one pot, then transplanted them into four separate pots. They have survived the transplant I believe, but one of the pots has a light-blue mold growing on the surface of the soil.

I'm not exactly sure what kind it is or where it came from, but the other three pots haven't shown signs of mold growth yet, and hopefully I'll never see any.

Each of the pots have the same schedule of watering and sun light (in response to a previous answer, likely over watered), they have the same soil found here. (It's a mixture of mostly that and some potting soil, but the potting soil hasn't been the cause in the past.

They're in small pots, and I'm living in a really small space so making a 5-gallon bucket of bleach-water isn't optimal. How can kill the mold in the pot, and prevent it from growing in the other three?

Answer 1

The answer to your second question, "how prevent it from growing in the other 3", is as follows:

• Move this plant away from the other three
• Disinfect your tools every time you've used on the diseased plant
• If possible, disinfect your hands too.

After you have saved the other plants, we can examine your first question, "How to kill the mold in the pot". Starting as an immediate measure, I agree with the suggestions made by Kevinsky. Id est, removing manually the mold.

But we do not have data on what this mold is. It could be an algae (Cyanobacteria), or a mold (fungi, like Phytophthora citrophthora, Penicillium italicum, or other else) or some lichen (fungi + algae). The colour is the same, more or less. To distinguish among them, we can start a cursory examination of view (texture and presentation are different), but an exact result we can have, possibly, from a microscopic examination.

Different causes require different remedies. I believe that a thorough examination would probably be too complicated. But certainly, I think, the mold is not only on the surface but also inside the ground.

So, to help you if you feel like it, you can

• Remove the plant from the pot
• Completely change pot and ground (for algae and lichens)
• Disinfect the bare roots and the stem with a fungicide (for fungi)
• Plant again your apple tree in an uncontaminated environment.

Try to do this quickly, without subjecting the roots to temperature changes or drafts. In this way, you deal with all the issues from various sides and it is possible, I believe, to solve them. This is what I would do.

Answer 2

This should do the job:

• Manually remove the mould from the surface of the soil
• keep the plant a little drier
• increase ventilation
• move to a sunnier location