Overworld vegetation, such as grass, flowers, saplings, etc... cannot be placed on muddy mangrove roots.
Since it's intentional that grass can generate on muddy mangrove roots as stated in
MC-249941, one would expect that you would also be able to place overworld vegetation on top of these blocks manually, however, this isn't the case.
- Place down some muddy mangrove roots.
- Obtain some overworld vegetation, for example, some flowers.
- Attempt to place the overworld vegetation on the muddy mangrove roots.
- Take note as to whether or not overworld vegetation can be placed on muddy mangrove roots.
Overworld vegetation cannot be placed on muddy mangrove roots.
Overworld vegetation would be able to be placed on muddy mangrove roots.