it happened to me once when i had a plant inside a greenhouse on the bottom shelf where the light couldn't reach the soil. once i took it out of the dark humid environment it cleared things up. never caused any trouble. i think that most soil contains spores that will pop up in the right conditions. i thought it was awesome lol.
Haha that's great, I grow some mushies on occassion and I have to say if the conditions were right, that is fairly impressive. And like he said, move them into the light and possibly decrease humidity. All the other things i can think of that will kill mycelium would also hurt your plants(i.e. heat, molds, water, etc.) Edit: Actually I just thought of this, pick the mushrooms before the caps open(as to not drop spores). Be sure to use gloves in case the strain is poisonous! If moved into the light and the humidity is decreased, the mycelium won't have a chance to regenerate after fruiting so it'll die out. Best of luck!
We are all breathing mushroom spores all the time. Yes mushrooms do thrive in humidity. However I have seen one grow that was more like a piece of wood... I had been neglecting it for a while, quit spraying it down and shit... Also mushrooms like great air circulation for fruiting as much as anything else. In fact most people advise upon having the air completely cycled out several times an hour for a mushroom grow. Pick em and throw em in the garbage. Psilocybe Cubensis will not grow in dirt. Prefers grains. And the azurecenes are a lot harder to grow. That is definatly pretty amazing, if you have a camera take a picture and upload to shroomery.org and have someone id it for you.
Let your soil dry out between waterings. If the shrooms don't have constant moisture, they will die out.