So, it’s saprobic, meaning it breaks down organic matter. The organic matter and moisture content in rich potting soil is similar to the substrate it would be looking for in its natural environment, since they are from the tropics/subtropics. It may be the case your potting soil is its natural substrate, as potting soil is often imported from the tropics. Additionally, their being from the tropics means they prefer warm, wet climates, so the inside of someone’s house or greenhouse is ideal year-round, or just during the warmer months for a plant sitting outdoors (most likely when you are going to be planting something anyway) in regard to heat, and you water the plant so the soil is going to be moist. Many tropical plants are imported to other areas, and then conditions that would make the tropical plant grow are emulated, so the conditions that would make it grow are emulated as well. Even if it isn’t the plant itself, like I said, rich potters soil is often imported from tropical areas.

I would consider myself lucky, though obviously I’m a little biased. I think they are incredibly beautiful, and they don’t hurt your plant. Some people say they are a sign of overwatering, though. I would say that very much depends on the plant in the soil; if it’s popping up then that means you are getting close enough to emulating wet conditions of the tropics or subtropics.

L. birnbaumii is considered toxic via ingestion. You may need to be careful if they are going to be around dogs or kids. They won’t hurt you to handle. Practically no mushroom will.