Leucocoprinus birnbaumii (luke-o-kuh-PRY-niss burn-BAUM-eee-eye) begin like teeny-weeny yellow dicks pushing up out of the soil of your house plants.
They like warm, moist soil (which is why indoor houseplants in the winter seem to get them the most).
Here, the leucocoprinus birnbaumii is happily growing in the bamboo . . . and some other fungus (mildew) is happily growing on it:
We also got these yellow mushrooms, which grew differently than the Leucocoprinus birnbaumii. They’re much more umbrella-like, and not very penile.
They’re attached to the bottom of two containers that came from a friend, so they might be something entirely different, or we might have missed the earlier manifestation, and they are leucocoprinus birnbaumii, just growing on the substrate of the planter cup.
Most everyone I’ve read on the topic has said, “If you have Leucocoprinus birnbaumii in your house plants, you probably live in a winter clime with little colour. They’re virtually impossible to get rid of, so just get over them, and learn to love the extra yellow in your life.” One author suggested putting some fairy dolls in with them.