The bug

When a sapling tries to grow (for example when using bone meal, or by being ticked), it tries to grow on the highest block in the x/z column it is located in. If that block is a block that it can grow on, the sapling will disappear and the tree will be generated on top of that block. If it isn't, the sapling will never be able to grow.

This issue seems to affect all types of trees except large oak trees, balloon oak trees, dark oak trees, large spruce trees and large jungle trees.

To reproduce

1. Plant a sapling on the ground
2. Place a stone block a few blocks above the sapling
3. Try to grow the sapling using bone meal
   → The sapling won't grow
4. Replace the stone block with a dirt block
5. Try to grow the sapling using bone meal
   → The sapling disappears and the tree will be generated on top of the dirt block