Why is mold forming on top of soil?

Question

I brought my Donkey Tail succulent into my house about 3 weeks ago and the temperature outside was 32 degrees, which I believe I remember doing last year also. But now I’m seeing a grayish mold forming on top of the soil. The pot is in front of a bay window with diffuse lighting most of the day, but it is pretty wet, probably too wet right now. But the plant looks really good currently, except for mold. What should I do to keep it healthy? I’d hate to see my plant die from it. I did add additional cactus/succulent soil on top of my plant this past summer, don’t know if that newest soil could be the problem possibly. Can you help me?

Thank you, Christine.

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Answer 1

Mold tends to grow in pots that are too wet. When you bring a potted plant indoors for winter, it will need less water than it needed outside, because it will be less active in the lower light levels indoors. Overwatering will cause plant health problems:
https://www.gardeningknowhow.com/plant-problems/environmental/signs-of-plants-affected-by-too-much-water.htm
https://www.gardeningknowhow.com/plant-problems/environmental/overwatering-container-plants.htm

Many succulents are especially sensitive to overwatering, so it is best to let the soil get dry on the top and about an inch down before you water each time.

The additional soil that was added on top may also be a problem, if it buried the base of the stems. That could cause the base of the stems to rot. I recommend removing that soil, or repotting the plants in cactus/succulent soil.