Question
Hi,
I live in the United States in Washington. I have six indoor plants. Three of them are dwarf Umbrella trees and three are spider plants.  We have them in terra-cotta pots. Today when I was watering the plants, I noticed tiny little black balls that came to the surface of the soil. I have seen and read about the white or cream colored balls, and know that they are time released fertilizer, but what about the black ones? Are they also time released fertilizer? I also would like to know what kind of liquid fertilizer I should use for these plants?

Thank you so much for taking your time to answer my question!

Answer
Salina
Without seeing the soil I can't say for sure. I do think they are residual fertilizer balls. Squeeze a few to see if they have liquid in them.
Most indoor tropical plants require you to add fertilize on a weekly to monthly basis during the growing season. Visit your local garden center (not chain store) and see what they recommend for your particular plant. Take some of the black balls with you for them to examine.
Good luck.
Rick in southern NJ