Giant Glowing Mushroom

Giant Glowing Mushrooms are similar to Trees, but grow randomly in Mushroom Biomes when enough space exists. They can be chopped down with an axe, which yields Glowing Mushrooms and, less often, Mushroom Grass Seeds. Giant glowing mushrooms also give off light, similar to Mushroom Grass and Glowing Mushrooms.

Giant Glowing Mushrooms grown in surface and underground biomes each have distinct graphics: Underground versions grow with plain, straight stalks, while Surface versions can display more complex branch formations.

They have similar requirements as trees:
 * The ceiling must be at least 16 tiles above the floor.
 * There must be no wall right on top of the floor for them to spawn, but there can be wall behind the floor and from 1 tile above it.
 * They will grow only when there's a flat patch of 5 blocks.
 * They will grow at least 2 tiles from each other.

Trivia

 * Although in changelogs these have been referred to as Giant glowing mushrooms, or simply Giant mushrooms, in the source code they are referred to as Mushroom Trees.
 * On the in-game minimap, they are simply labeled as trees.