Place birch sapling.
Place block WAY above it.
Bone meal it for a LONG time and observe how it won't grow
This is a major issue as it makes tree ungrowable in the nether and breaks a lot of tree farms.
MC-164721
Trees need skylight 15 to grow
Resolved
Duplicate
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Does MC-164143 describe this issue? If the block way above isn't suitable for growth, the sapling won't grow