Leaves

Leaves are a type of block which grow as part of trees. There are six types of leaf blocks, one for each of the six types of trees (oak, birch, spruce, jungle, acacia, and dark oak), which are identical except for their appearance and their drops when destroyed. Leaf blocks are easily destroyed by tools, explosions, and fire, and when destroyed may drop saplings which can be used to plant new trees.

Leaves have no use in crafting.

Appearance
Leaves take on a different shade of green depending on the biome in which they are placed.

Leaves are always transparent to light but cannot be seen through when the graphics mode is set to "Fast"; the transparent regions are instead black.

Leaves diffuse sky light, causing the shadows they cast under trees. The light level from sunlight or moonlight is the same in each block of air in the column of air above the highest obstruction in the column. When placed, leaves obstruct that light column so that the lowest air block above the leaves acts as other light sources do. As you descend below the leaves, the light level diminishes with distance like it would from other light sources such as torches. To control this effect, create an opaque 1x1 column-tunnel with leaves at its opening above you.

Decay
Leaves from trees spontaneously decay (disappear) randomly when not connected to a wood (log) block by other leaf blocks, with a maximum distance of 4 blocks. Decaying leaves will drop saplings and apples at the same rate as directly destroyed blocks. The supporting wood block doesn't need to be of the same tree type. Player-placed leaf blocks will never decay and can be used in construction such as tree houses and hedges.

Drops

 * When harvesting using shears or a Silk Touch tool, leaves drop as themselves and can be placed elsewhere.
 * Leaves which decay or are destroyed without using shears usually drop nothing, but yield saplings 5% (1/20) of the time. Jungle leaves drop saplings 2.5% (1/40) of the time.
 * Oak leaves also have a 0.5% (1/200) chance of dropping an apple.
 * Leaves that are burned do not yield saplings or apples.

Data values
Block 18

Block 161

Original leaf decay algorithm
In Alpha, leaves would decay using an algorithm that checks whether it has a solid or leaf block underneath it or is adjacent to a solid block. If it doesn't, it must be connected to a leaf block that is also supported as long as it is no further than five blocks away from said support.

Trivia



 * Occasionally, leaves will grow through other blocks, acting as though they are still connected to the tree. They may also completely replace blocks they try to grow into.
 * Leaves do not prevent a sapling from growing. As long as the five blocks above a sapling are transparent, the tree will grow (provided it has enough light).
 * In the default textures, the leaf to air ratio for the texture is about 3:2 for normal/birch leaves, and about 9:5 for spruce leaves.
 * Leaves do not prevent chests from being opened, even when running in "Fast" graphics mode. See Opacity.
 * Despite being highly flammable, leaf blocks cannot be used as fuel for a furnace.
 * Some trees seem to occasionally drop apples or saplings without being destroyed due to creation of leaf blocks not supported by wood.JungleLeavesTex.png
 * Leaves were the first block in the game that gave you a different item depending on what tool you used to harvest it (shears or hands)
 * There is no real difference in amount of apples or saplings dropped from leaves when they decay naturally versus being destroyed by the player.