Read more: The Most Common Myths About House Plants Debunked Beneficial molds that help break down organic matter in the soil ...

You might assume that fungi are always bad because many are pathogens that cause plant (or human!) illnesses. But, what’s typically growing in houseplant soil is a type of saprophytic fungi.

Bacteria and saprophytic fungi break down complex carbon compounds in dead organisms, faeces and urine into simpler carbon compounds, returning them to the atmosphere or soil.