When grown with bonemeal on floating grass, there is a chance that the leaves will generate below the level of that grass
Steps to Reproduce:
1. Place a 2x2 platform of dirt some height above the ground
2. Place 4 spruce saplings on the dirt
3. Spam with bonemeal
This may require some repetition, because it only happens with the 'conical' spruces.
This was marked as a duplicate to a rather different bug, even though they are not the same problem. The problem there is that the top of the tree looks strange, the problem here is that the bottom of the tree is in the wrong place.