Saplings

The glass sapling is used to grow the glass tree. It just uses the glass texture and doesn't have any sapling shape to it what so ever. However, when placed down it does what the normal sapling does with the texture.

Glass saplings can only be placed on normal glass, not even stained glass. You can use bonemeal to grow it into the tree.

Despite there being a bone tree, it does not come with a sapling. There is one in the code, but isn't registered in the game. This is for testing. The deadwood tree also doesn't have a sapling. However the manchineel tree does.

Obtaining
It can be obtained from breaking leaves.

Usage
To grow trees. It is unknown if you can place one in a flower pot.