Mold growing on outside of clay pots

[josterha]

Hello All,

It's been a while since I posted, but I was hoping I could get some advice on this problem. I have six different pots sitting on pebbles in a humidity tray in my living room. I noticed the other day that there was a powder-ish substance on the outside of the pots. After I watered, it turned into a full-blown bluish mold. I think the same type of mold that you might find on old bread.

What should I do? I am allergic to mold, so I want to get rid of it ASAP. I am having allergy attacks. I read somewhere that many orchids use some fungi symbiotically in order to synthesize food (?). I have phals and oncidiums in the tray, and they all seem healthy. Most have been recently re-potted as well.

Should I add clean-out my humidity tray, possibly with bleach? Can I add anything to the water to kill the mold, but not harm the orchids?

I await your sage advice.

Thanks,
John

[Tsuchibuta]

I would just spray with a fungicide, or get some physan 20 and wipe down the pots. There are all kinds of fungicides on the market safe for orchids and I'm sure there are some "organic" methods as well. If you are really allergic to the mold I would recommend repotting into plastic as fertilizer and other minerals get trapped in the porous clay and that is what the mold is feeding off of. Eliminate the food source and you'll eliminate the mold. Until then you'll always have fungi to some degree though not always visible to the naked eye.

[Lagoon]

Don't risk you're health, dump the clay pots and go with plastic.
Looks like we share the same problem. Over the last 6 months ... I've repotted all mine from clay to plastic pots.

[Judi]

I haven't had this problem with mold, but I often wonder about the plastic humidity trays I have--it doesn't take long for them to smell really bad, and when I dump the water to clean the trays there is always a slime in the trays. Is this a type of mold? How often should the trays be cleaned, and should I dissenfect the trays before I put in clean water ? We have hard well water.

[masda]

Water in humidity trays should be changed every otherday to prevent it from becoming stagnant which is why it turns slimey, also clay pots will hold salts and other residue if they have been used before and should be soaked in a sterilizing solution befor use.

[Ross]

For me, Physan 20. Works every time.

[cirillonb]

If I had to change the water in my humidity trays every other day I would give away my orchids and do something else. To avoid the vile soup that these trays become, I fill them with a solution of Physan-20 1 tablesp (15ml) per gallon water (4L). You could use bleach (I don't know the dilution) but I always seem to get a drop or two on my clothes when I use bleach and you know what that does. Furthermore, I wonder what a steady diet of bleach would do to the plastic trays that I use.
Also, some of the stuff in the humidity tray is dust from the house.
Nick

[Judi]

Thanks, sounds like I will have to get some Physan 20!