Hi. I need some advice and I hope you guys can help me. I'll try to explain my problem in detail.

I keep all of my 40 plants in terracotta pots with drainage holes. I water them only when they get bone dry (usually once a week-10 days) and I do that with all of my plants, even the ones that like to be moist all the time. So I let everything dry out. I have some plants like a peace lilly or fittonia that droop a lot and tell me that they are thirsty. Usually I use a moisture meter to see what is ready to be watered. So the soil is NOT soggy all the time. I do have a heavy hand when it comes to watering. I've seen so many videos about watering plants and read so many tips about watering, so I always give them a good drink. I pour water two or three times until it comes out of the drainage hole. I never let the pots sit in water. My plants are in bright indirect light in front of a west facing window.

So why do I have this mold/fungi problem?(see pictures) It doesn't matter what I try, the mold pops up. I change the soil surface, it comes back. I've read about soil aeration, so I finally found a bag of perlite and mixed it in my soil (I use normal store bought soil because there is nothing else to buy in my city and country. I guess not a lot of people have this hobby). But the mold stayed. I even repotted some plants in new soil and it is still there after watering. I tried to bottom water my fittonia, so the top of the soil wasn't even wet and yet the mold came back. I sprinkled cinamon on the soil and it didn't help. The last time I watered this fittonia I tried using less water and the mold still came back. But the problem is not just the soil surface. I get the same typle of mold on the outside surface of my pots after I water. so everytime I water a plant I have to wipe the pots for days until the soil gets dry and the mold stops showing up on the pots, which is very exhausting to be honest. I used to love watering my plants but now it is just so much work. The pots always look so moldy and messy and I want my plants to look nice. I have to clean the soil surface on every plant and wipe the pots a milion times until the plant gets dry, but by then, it is time for the next watering..the only plants that dont have this problem are my succulents, sansieveria and zz plant, that I water once a month. what am I doing wrong? This is just one rando photo, I have plants with a bit more mold than this

It looks like sponge rock to me. I use Miracle Grow potting soil and these white pieces of various sizes help with drainage and aeration in the soil.
It would explain why you can't get rid of it because it is part of the soil.

It does appear that you have some sort of fungus/mold growing there. Does the plant get good air circulation? Maybe a fan would help. Sounds like you're doing everything else right.

I see the mold. But, it may be in the potting soil you are using, especially if it keeps coming back. Are you buying bags of new soil? Or using old or recycled soil?

You may have to sterilize your potting soil before using it. But, if the mold spores are in the air, there's not much you can do.

How is the climate in Bosnia? Is it humid? Is Bosnia known for Sourdough bread? Do you have a fan so you can get the air moving around your plants?

@Daisyl I don't really know how humid it is here. I never thought about it. I guess it is normal. Not too humid, not too dry. Usually when I bring a new plant home, I use new soil to repot it in a terracota pot. Plastic pots don't work for me at all. Sometimess I have some soil leftovers so I use that if there is no need to buy a new bag. I usually buy only small bags of soil, so it doesn't lay around for long before I use it up. In Bosnia we only have about three brands to choose from, so I buy any of them, it depends what I can find at that moment.

@ctcarol I have an air condition above these plants. Does this count? It was on during the summer and the mold was still there. I even use a stick to loosen the soil from time to time, so it doesn't become too compacted.

Since I have a few plants that are tropical plants and need high humidity, I mist them every morning. And as I said, I have a heavy hand when it comes to watering, so I mist heavily too. I guess that some of the water I spray gets into all pots that are around the plant that I am misting. can this be the cause of it? To be honest the mold on the soil doesn't bug me as much as the mold on the outside of the pots. It is like the water comes trough the pores of the pots and mold builds up and it doesn't matter how many times you wipe it off, new mold appears untill the plant gets dry and there is no humidity left. when you combine these two issues, watering becomes very exhausting and messy. the pots become white and sticky. it is not a pretty sight and it ruins the overall look of my beautiful plants. they are beautiful indeed 😁

The mold on the pots is different than the mold on the soil. The pot mold isn't really mold but salts and minerals leaching from the clay body. Some brands of clay pots are worse than others for this. You can eliminate this by using plastic or glazed pots.

If this chart is any indication, you have very high humidity year 'round.
https://weather-and-climate.co...

Maybe you should stop misting.

@Daisyl I will exchange the top soil on my pots and stop misting for some time to see what will happen. Thank you!

Never use used soil. In fact, it is best to use sterile, soilless, potting mixes that are usually free of mold spores. You may be following water instructions carefully, but if your plants are in pots that are larger than necessary, then the soil will stay moist for too long. I doubt that humidity is a problem.

Thank you Daisy! I was debating posting the same . We have hard water here, and after a period of time the salts etc. do leach through the terracotta pots, leaving a whit film.

Some terra cotta turns to slime in days. I looks for pots that aren't so porous. Those are salts and minerals leaching out of the soil through the pores of the pot but also from the clay body. Double Whammy!

Here is an answer from the NGA Knowledge Base written in 1989:

"Part of the beauty of terra-cotta pots is the character they develop as they age. Some of this character is in the white streaks and green mold that they develop. Since terra-cotta is porous, moisture is constantly being drawn from the soil to the outside of the pot where it evaporates. This is good for the roots of your plants but it also sets up just the right environment for mold to grow. The mold is relatively harmless, and outside of sealing the pots inside and out, there' s no real way to prevent it. You could put your plants into plastic containers and place those containers into the terra-cotta pots. That way the decorative pot will remain dry and free of mold."

I think it's because of the humidity. I had a similar experience and unfortunately, I couldn't save my plants. And so, I have a greenhouse and a small room where I store heat-loving plants when it's cold outside. At first, I noticed some unpleasant smell in this room, and after a while, mold appeared on the walls and ceiling, which spread to some plants. I know that mold is destructive and dangerous to health because it can cause serious respiratory system health issues. That's why I called a local mold removal company to get rid of the mold. I was able to cure some plants, and some died. So if you see mold, you need to act quickly to remove it.

(Thread over a year old)