Tree

Trees are built of Log and Leaf blocks. When generated by the map, they are frequently found in groups forming a forest. Tree generation was added in version 0.0.14a. Players in Creative Mode can build their own ersatz trees.

Trees come in 3 different heights and do not all grow exactly the same. In Alpha, large trees can grow boughs or branches. Trunks and boughs can be harvested for Wood (Logs) without any tools. The treetops are not subject to gravity and will not fall if the trunks are removed. Leaves and logs are flammable, and forest fires spread easily if trees are touching.

Breaking leaf blocks can produce saplings which are collectible. If a sapling is placed in sunlight on a grass or dirt block with enough space overhead, a tree will usually grow the same day.

Sapling growth was added to Creative Mode in version 0.28_01. Due to griefer-friendly applications ("treespam"), a grow-trees flag was added to server.properties of the server files.

Indev Trees
Currently, in Indev mode, trees wither and die if the leaves no-longer have a connection to a piece of soil below them and lost their connection to a tree trunk on the same height. The tree trunk can be cut from under the leaves to have a floating tree top. Low-lying trees will sometimes leave pillars of leaves that touch the ground and will not wither.

When planting trees in Indev mode they do not require grass to grow and must be planted at least 3 blocks away from other obstacles, they take around 1-2 minecraftian days in order to reach maturity. They can also be grown anywhere that sufficient light and space exist, including underground with torchlight.

After some research it was shown that when saplings are planted near trees they usually grow bigger.

Infdev Trees
Infdev now has some changes with respect to the code used in indev. Leaves wither when not in contact with a trunk or the ground and will occasionally drop saplings.

A Sapling should be able to grow into a Tree as long as it has:
 * Sunlight -or- an adjacent Torch
 * 4 empty spaces directly above the sapling block itself
 * Leaf blocks count as "empty space" for tree growth

Some factors that were tested and still allowed saplings to grow into trees:
 * Sapling being surrounded by blocks or torches
 * Sapling having only one adjacent torch in an otherwise enclosed, dark room
 * Sapling being planted next to another sapling
 * Sapling being planted next to a fully-grown tree (assuming that any leaves above are cleared)
 * Sapling having a leaf block directly above it, with 6 more leaf blocks above that one.

Saplings will sometimes fail to grow for no reason, or take an exceptionally long time to do so. The above factors have been tested, but your mileage may vary due to the random aspects involved. It's possible that trees will grow faster or more readily when given more space. At the very least, trees can grow with just light and 1x1x4 headroom.

Helpful hint: Looking straight up and mining/digging until you can no longer reach will clear a little more than enough space to plant a sapling at your feet and give it sufficient room to grow.

Random note: If a tree grows next to or under glass, its leaves can spawn inside the spaces occupied by the glass blocks. If this happens, those glass blocks will be destroyed.

Leaf growth can also destroy torches.