When a mangrove propagule grows it replaces mud and muddy mangrove roots.

Steps to Reproduce:

1. Place walls of mud or muddy mangrove roots around a mangrove propagule
2. Bonemeal the propagule

Observed Results:
Mud turns to muddy mangrove roots where mangrove roots generate as expected, however it also gets replaced by leaves and wood elsewhere.
Muddy mangrove roots gets replaced by mangrove roots, leaves and wood. 

Expected Results:
Mud is not supposed to be replaced by mangrove leaves and wood when a mangrove tree grows. 
Same goes for muddy mangrove roots. They're expected to not be replaced by mangrove roots, leaves and wood.

Consequences:
Some mangrove tree farm designs are affected or don't work at all due to this bug.