Mangrove trees will fail to generate if their roots do not hit a solid, unreplacable block before reaching their maximum root length; attempting to grow a mangrove tree over void/at the very edge of a floating island (for example, using the end dimension), or in a world without a bedrock layer and all made of mud/air, will cause generation to fail.
Removing mud from the "MANGROVE_ROOTS_CAN_GROW_THROUGH" tag nullifies case 2, and mangrove trees generate properly in that instance.
How to replicate:
Case 1, through air:
- Place a single dirt/mud block suspended above a void (end for ease) or at the edge of a floating island (end for ease)
- Place Mangrove propagule, apply bonemeal
- Tree fails to generate (fig. 1)
Alternatively, using /place feature minecraft:mangrove will provide feedback in the chat window (fig. 2)
case 2, through #mangrove_roots_can_grow_through:
- Create a superflat world with any number of mud blocks
- place mangrove propagule, apply bonemeal
- tree fails to generate (fig. 3)
Alternatively, using /place feature minecraft:mangrove will provide feedback in the chat window (fig. 4)
Expected behaviour
Mangrove trees generate properly above voids, with hanging roots.
Does MC-250070 describe your issue?