White mold on terracotta pot exterior - Orchid Board

Salixx · #1 11-07-2016, 08:48 AM

A little while back, I experimented with a Masd. chaparensis in s/h and a regular clay pot to increase evaporative cooling on a plant I couldn't quite give the temps that it wanted.

From the plant's perspective, it has been a success. Shortly after the repot, I had an explosion of new growth. I have since (and plan to continue) to use this method for my other cool and cool-pref growing pleuros. I currently have three different masdies in clay pots and want to do more.

The only real "problem" I have run into is the growth of white fungus/mold on the exterior of the clay pots that looks like hard water deposits. I don't care all that much about it, but it is quite slimy and gross to handle at watering time. I have been wiping it off with a cotton ball soaked in 95% isopropyl alcohol. This has curbed the growth, but not eliminated it and I still have to do it every one to two weeks.

Are there any more 'permanent' solutions to this? I am looking to cut time spent on things that aren't necessary while not causing harm to my plants and potential beneficial bacteria and fungus that may be in their root system.

Thanks for any help!

estación seca · #2 11-07-2016, 09:17 AM

It' probably not mold, but mineral deposits from water evaporating. Sodium salts give a slimy feel. Try wiping it off with a dilute vinegar solution instead. The salts are more soluble at an acid pH.

Salixx · #3 11-07-2016, 09:37 AM

It's possible, though it looks like fungal growth in some spots. I'll see if I can get a picture to be sure. In any case, a concentrated does of vinegar would probably kill a fungus just as well as alcohol, so I haven't got anything to lose!

I will add, I only water these guys with RO water and very diluted ferts which it why I didn't think it was mineral deposits. I could definitely be wrong though.

estación seca · #4 11-07-2016, 09:49 AM

The pot had minerals in the clay when you bought it. And it doesn't take a high concentration of minerals in your water to cause the efflorescence. All the minerals in all the water are carried by the evaporating water to the outer surface.

Most of the evaporation from the pot takes place from the clay surface, which is larger in aggregate than the opening at the top. You water the medium so you wash the salts there back into the pot.

Salixx · #5 11-07-2016, 09:52 AM

Here's a picture. I couldn't capture the texture, but you'll get the idea.

estación seca · #6 11-07-2016, 10:09 AM

Yes, I think it's mineral efflorescence. The vinegar I suggested would be dilute - only enough to lower the pH of the water to increase mineral solubility. Lots of vinegar will provide a carbon source. Algae will go wild on the outside of the always-damp pot. Talk about slippery!

Tindomul · #7 11-07-2016, 11:59 AM

I had the same, for now I am just scrubbing them off with a brush.

---------- Post added at 11:59 AM ---------- Previous post was at 11:59 AM ----------

Quote:

Originally Posted by estación seca

The pot had minerals in the clay when you bought it. And it doesn't take a high concentration of minerals in your water to cause the efflorescence. All the minerals in all the water are carried by the evaporating water to the outer surface.

Most of the evaporation from the pot takes place from the clay surface, which is larger in aggregate than the opening at the top. You water the medium so you wash the salts there back into the pot.

Thanks for this, I was a bit worried with mine concerned that I was over fertilizing my Masdies.

Salixx · #8 11-07-2016, 12:27 PM

Thank you as well! I am relieved that it's probably not mold. I will take minerals over fungus any day.

estación seca · #9 11-07-2016, 12:35 PM

Fungus growing on dead organic matter, like dead leaves or wood, generally doesn't attack living plants. Such fungi are called saprophytes. The fungi attacking our plants don't live on dead organic matter, but only in tissue of live plants. If I had to choose I would rather have saprophytes than mineral deposits.

Salixx · #10 11-07-2016, 01:07 PM

Oh, I knew the plants would be fine. I was more concerned with my boyfriend and I just in case it had been a type of mold that would irritate our allergies...

Of course, now that I think about it, the humidity in the room is overall more likely to cause those issues. Good thing the bf is the human equivalent of a Masdevallia! 60% + humidity at night or he pouts!