Mold and mildew are types of fungus. They grow from tiny spores that will float in the air from one place to another. They produce millions of spores. Once you have a mold or fungus infestation, it is very difficult to get rid of but can be controlled.
Fungus likes higher temperatures ( 75 to 90oF), high humidity, stagnant air, and darkness. If we control these factors, we will have some success in controlling the fungus.
1. Keep the temperature in the lower range (60 to 70oF). The mold will not grow as well at those temperatures.
2. Usually it is not difficult to keep the humidity at an acceptable level. Too high a humidity is often caused by overwatering or using plant pots without drainage holes in the bottom.
Always make sure that the plant has dried sufficiently between waterings. Test the soil with your finger down at least 1 inch (2 inches in pots 10 inches in diameter or greater) If the soil is not dry that far down, the houseplant does not need to be watered yet.
If the pot has no bottom drainage, the soil will remain much moister lower down in the pot. The water has no where to go but up and will raise the humidity near the surface of the soil.
3. While it is best to keep most house plants out of drafts, some air movement is needed. This circulation will disperse the oxygen and humidity given off by the plant throughout your room and replace the air around the plant with new room air. This will benefit you and your houseplant. It will also help dry out the surface of the soil where the fungus will start to grow.
4. Mold and fungii grow best in darker conditions. If you place your houseplant in a brighter location, the mold will not grow as well.
These are just some of the methods we can use to discourage the growth of mold and fungus on the soil around our houseplants.