Huge mushroom

A Huge Mushroom is a naturally occurring structure composed of several blocks: mushroom stalks and either red or brown colored blocks for the cap. These blocks provide a valid spawn area for hostile mobs, and may be destroyed by hand to yield 0-2 normal mushrooms. The texture for the blocks which make up the cap depends on their position on it; for example, the corner block of the brown variety has 3 sides with the brown texture and 3 sides with the pore texture, while a block in the middle of the cap has only its top face covered with the brown texture and the others covered with the pore texture.

Huge mushrooms occur naturally on Mushroom Islands.

Growth
Huge mushrooms can be grown by applying bone meal to a small red or brown mushroom that is planted on dirt, grass, or mycelium; this works in any dimension. Can only be grown in darkness (except if grown on mycelium.) (Note that only the small mushroom's original square needs to be dirt/grass/mycelium.) The axe is the best tool for destroying huge mushrooms. When destroyed, large mushroom caps and stalks have a chance of dropping small mushrooms of the same type they were grown from. Each giant mushroom can be expected to drop 2-25 small mushrooms, making this a valuable source of food.

A huge mushroom, brown or red, may grow to be 5, 6, or 7 blocks tall; no taller or shorter. They require a 7×7×6 to 7×7×8 space to grow depending on their height, not counting any spaces occupied by torches, ladders, etc. However, the bottom-most layer (where the mushroom is placed) only requires blocks immediately adjacent to the source mushroom to be free, not counting diagonal blocks.

A huge mushroom will only grow if there is sufficiently low light, or if grown on mycelium. Attempting to grow a mushroom in an area with too much light will not use up any bonemeal.

Whenever bone meal is used on a mushroom, it randomly selects a size to attempt to grow. The maximum height that will succeed is one less than the amount of free vertical rows available above the mushroom; thus, if a block is placed 7 meters above the mushroom, anywhere in the 7x7 row, it can only grow to be 5 blocks tall. If the game selects it to be 6 or 7 meters tall, the bone meal will fail on that attempt, similar to how it behaves with tree saplings. This allows the player to force huge brown mushrooms to always be 5 blocks tall, but may consume significantly more bone meal due to failures.

A huge mushroom will not grow above the height limit/skybox without modifying the game. They can be collected using the Silk Touch enchantment. When mined that way, huge mushrooms will drop only blocks with spores on all sides.

Huge brown mushrooms
Huge brown mushrooms consist of a single stalk in the center, with a 7×7 canopy of brown mushroom blocks at the top with the corners missing.

Due to the space requirement matching the size of the canopy at the top, it is possible for a huge brown mushroom to grow with its canopy directly touching a mushroom next to it. This gives explorers the ability to quickly assemble platforms out of huge brown mushrooms, which affords a sleeping platform safe from mobs when illuminated (a single torch in the center is sufficient) or even the base for a house.

Huge red mushrooms
Huge red mushrooms, like their brown counterparts, have a single stalk in the center, but a different canopy, composed of five 3×3 slabs of red mushroom blocks arranged above and around the stalk, forming a 'dome'. Even though the space requirement is the same, the actual huge red mushroom only ends up being 5×6 blocks in area, so subsequent ones can be grown closer together than brown ones.

Due to their shape, huge red mushrooms can be used to build a basic hut, either by filling in the space between the cap and the ground, using pistons to push the cap of the mushroom to the ground, or by digging a large enough hole to accommodate a huge mushroom so that the cap intersects with the ground (may take multiple attempts; see above). Due to the height mechanics, one can always force them to be 5 blocks tall with a block 7 blocks above, so one can simply dig a hole in the ground, place a red mushroom, and dig out the 4 adjacent holes. While this may also take multiple attempts, the resulting huge red mushroom will be guaranteed to properly align with the ground.

One way of growing a red mushroom on the surface of the world at any time of day without mycelium (using bone meal) is to dig a tunnel starting from several blocks where the mushroom should sprout, and plant the mushroom two or three blocks below the surface at the end of the tunnel. Then dig a single block chute to the surface from above the mushroom. If the mushroom is deep enough underground, it will not pop off when exposed to the light above it. Once there's light, use the bone meal and see if it grows the mushroom. If it does not, there may be too many blocks in the way of the mushroom, in which case, planting the mushroom closer to the surface may make it grow.

Placing blocks where the inside of a red mushroom would be does not hinder the growth of the mushroom substantially, only if the blocks are directly in the way or lie outside of the mushroom will it not grow. By placing dirt blocks around where the stem of the mushroom is suppose to be, you can block the light allowing you to place the mushroom even closer to the surface - then fill up your tunnel and remove the dirt inside of the mushroom once it's grown.(Minecraft 1.4.6)

History
In a tweet, Notch showed a picture of a Beta 1.7 change-list (back then Beta 1.8 was planned to be Beta 1.7). Although it was completely blurred out and was at first thought of as a joke, Notch later stated that one of the pictures with the new lighting system and the change list had a secret in them. People all around the web started speculating.

One place where people discussed it was on the Minecraft Forums, where it was discovered that the tabs at the top of the change list, which were partly covered, could be decoded based on the one pixel tall pattern available in the image. After a user named "tmcaffeine" successfully decoded the image, the tabs read: ExperienceOrb.java, changelist.txt, Level.java, Tile.java, HugeMushroomTile.jav(a?), HugeMushroomFeature.(java?), RandomLevelSource(cut). This led people to believe that huge mushrooms would be added, and indeed, later on Notch revealed a screen shot on Google+ in which two huge mushrooms could be seen as well as an NPC Village.

In the Beta 1.8 pre-release, huge mushrooms did not generate naturally, but could be planted by the player by using Bone Meal on a red or brown Mushroom planted on dirt. In the pre-release version 1 of Beta 1.8's Creative Mode, the blocks composing a huge mushroom and bonemeal were not included in the item selection menu. The only way to create huge mushrooms in this version of Minecraft is to give yourself regular Mushrooms and a bone, craft the bone into Bonemeal, then plant the mushroom and finally use the bonemeal to grow a Giant Mushroom.

Up to release 1.2.3, different mushroom cap types could be created in survival by using the block damage changer exploit with any huge mushroom block as the default block. This was patched in version 1.2.4.

Trivia

 * If farming giant mushrooms indoors, use a 9x9x8 space, since torches on walls block mushrooms and the extra space is needed. Alternately, put torches in a one-block deep niche set into the wall.
 * The texture used for the sides of the stalks is a re-colored version of the bark texture used for spruce and oak wood.
 * If bonemeal is used to grow a huge mushroom, it can grow where the player is standing, causing the player to take suffocation damage.
 * The huge mushroom can be used as an emergency shelter. If a player has bonemeal and a mushroom, he can grow one instantly and sleep inside it after blocking off the bottom, surrounding area.  This makes bonemeal and mushrooms ideal to have for adventures away from home.
 * Huge Mushroom blocks with a data value of 15 have a texture that has the side of the stalk on all sides.