Stephanie

Is it mold for sure? Most often, it is efflorescence (that's what it is IMO): leaching of the calcium if using hard water, and salts/minerals from fertilizers. It doesn't kill plants. It is much better if those elements leach out rather than stay in the soil - if they accumulate in the soil, there is a chance of burning of the roots. I don't think that the roots will burn completely, and if you flush regularly, it will wash the salts build up away. It is, for many users, desirable or at least not a problem - many consider it a patina. It is difficult to get rid of. You could try to clean it off with vinegar or some bleach. In my experience, it usually comes back...

If it is actual mold, you may have very water retaining soil in the pot that helps mold to grow. That would kill the plant. Water retaining soil is not good for succulents, and you should repot them using fast draining mix.

You could spray paint the pot. That would stop efflorescence from showing up and solve cosmetic 'problem' - but if soil is water retaining, it would not solve that problem. You could decrease those stains on terracotta pots by using distilled water (or Reverse Osmosis filtered), and decreasing use of fertilizer. And washing exterior of pots regularly. I do not know if you can get totally rid of them.

I was thinking it was the leaching too Rina. I have never been able to clean it off completely.

Gabby - I do not think you can completely...there was time when I tried over and over again. With vinegar, and with bleach. I got used to it after a while, haha. And I do not use many terracotta pots anymore, because they break easy and are heavier. Even using distilled water, there still will be some leaching of minerals and salts found in the mix, and from fertilizer.

Im going with gabby on this. I attempted to grow salt crystals. In a terracotta pot. Crystals began forming on the outside of the pot.

Gabby C - Yes, unfortunately at the moment because we have been traveling a lot and that's all I have at my mother's place (where I had moved them from home, where i use distilled water)

Thanks everyone!

I have to say I'm a little less worried now. I'm definitely going to try the stuff you all mentioned.

Just salts leaching through the pot. You can get rid of it by using "lime away" when you scrub pots (not with the plant still in it, though).

Stephanie

If you don't mind, I want to point out what you said in your op:..."It has only caused one plant to die a couple months ago...so far"...

It may be good idea to check soil used. Potting mix for succulents should drain fast and well. I do not know what exactly killed your plant, but certainely not the efflorescence; it could have been rot (that is what happens very often). If your plant is still in original soil it was purchased in, there is very good chance that it is all or mostly peat. If you repotted it and took all old soil off the roots (that should be done when repotting), and used soil that drains poorly, that could, and often does, cause problems for suculents. They usually tolerate more of dryness than moisture. Just wanted to point this out...

I repot all my plants within a couple days of buying.

it was mold that got ahold of the dead plant, that's why I was worried

Sometimes the terracotta do grow mold on the outside of the pot and that has never harmed my plants either. The mold wipes right off.

Stephanie

What do you use to pot your succulents in?

Unfortunately, lots of bagged soil is not as well draining as advertised. Ppl using Cacti & Succulents bagged soil add lots of sifted perlite (or pumice if available) to it - mixing it 1:1. There should be no layers of different substrates, they should be mixed thoroughly. That would result in mix looking like this - C&S soil+perlite (photo borrowed from a member here):

There is some perlite in bagged mixes, but not enough to be of any benefit. There are many other mixes one can use - point is to get excellent drainage. Mold-rotting start most often with poor drainage (water retaining soil will do that...)