Question
We have a ficus plant (indoor) that's about 15yrs. old. In the last 2 weeks we have discovered that the soil is molding, which has created mushrooms to grow. What can we do to get rid of it, and to prevent it from happening  again?

Answer
You will find that many commercial potting soils are manufactured out of organic matter.  Fungi are Saprophytes that are always a part of this composting process.  Mushrooms are the "flower" of Fungi -- "Lepiota lutea" is my guess what you have in this case -- that are ready to reproduce.  These Lepiota were probably in your soil all along and are thriving with the pH, moisture and low light.

It is understandable that a person would be a little freaked out by this discovery.  They are unsightly, but they may not be harmless.  I would consider them hazardous to pets and children.

Conceivably, other plants growing in your house are the source of these spores.  They fly all over the place, including our lungs, out the window, into the hall, down the street, literally they are everywhere.

Ficus do not have to be kept so moist or in such low light.  Brighten their day and dry out their soil and they will not grow 'shrooms.  Raising the pH will also help destroy your mushroom farm.  Avoid coffee and coffee grounds; slight liming of the soil and a dryer, sandier growing medium will improve your odds.  If that doesn't work let me know and we'll discuss WMDs.

Thanks for writing.