Melon

Melons were first introduced in Minecraft 1.8 Pre-Release, the Adventure Update.

Behavior
If destroyed, melons will drop 3-7 (average of 5) melon slices. Melons will also be destroyed when a Piston of any kind pushes a melon block. If you put seeds and sticky pistons in the correct places it might be possible to auto harvest your melons. Each will heal one food point.

A melon slice can be crafted into a melon seed to be planted as a new stem. See also other plants.

Crafting
Melon blocks can be crafted out of 9 melon slices.

Farming
Melons will have a central stem that slowly grows until it reaches its maximum size at which point a melon will spawn on one of the adjacent farmland blocks. The stem requires an Air block or a Fence block above it to produce melons, the resulting melon does not. Melon stems take around 10 to 30 minutes to fully develop. Melons will revert the farmland below them to dirt when they grow. Melon stems will only grow a single melon at a time, but once their melon is harvested, another one will grow in its place. Any stem adjacent to a melon block will appear to connect to it. Bonemeal will cause a melon stem to become fully-grown, but will not produce a melon immediately. Melons are found rarely in worlds generated after the 1.8 update.

Farming can be made faster and easier by placing an up-facing sticky piston under each farmland block reserved for melons. When the sticky pistons are powered, they destroy all of the melons.

For maximum melon per block yield, the following methods can be used:

o o o o o o o o o           o o o o o o o o o            o o o o o o o o o     o o o o o o o o o            o o o o o o o o o            o o o o o o o o o o o o o W o o o o     OR     x x x x W x x x x     OR     o # # o W o # # o o o o o o o o o o            # # # # # # # # #            # # # # # # # # # o o o o o o o o o           o o o o o o o o o    9x8 @48.61%                   9x9 @44.44%               9x9 @44.44-49.38%
 * 1) # # # x # # # #            o o o o o o o o o            o o o o o o o o o

# = Melon Seeds; o = Farmland; W = Water; x = Any Block

With all these, both farm blocks and seed blocks will be hydrated.

The left method has an efficiency of 48.61%, the middle is efficient at 44.44%. The efficiency of the far right design varies (see below about designs that use the 'X' spaces).

Depending on circumstance (i.e. if you plan on making only 1 farm with no adjacent other melon farms) the latter 2 setups will be more efficient.

Wheat could be grown in the spaces marked 'X' to avoid wasting potential hydrated farmland blocks.

Designs that, instead, use these 'X' spaces for more melons introduce ambiguity. There would be seeds with two spaces to grow into. Such a design would sometimes be more efficient than the others, and sometimes only equally as efficient.

History
Melons were first revealed in an IGN interview with Notch.

On the Getsatisfaction.com complete ideas for the Ideas section, it was stated that Watermelons were to be implemented.