It must look like a traditional mushroom, with a central stalk and a cap above it. (A puffball counts if it actually has a visible stalk.) It must rise at least 1 meter from the point where it's last supported by the ground or another object. (The cap is counted in this height). This refers to actual vertical height as found in the wild, not the length of the stem when stretched out.

Resolves YES if anyone provides a credible example, otherwise resolves NO at close. Any mushroom that existed at any point before close counts, even in the distant past. (I must be highly confident that it actually existed, was a fungus, and looked something like a modern-day mushroom.)