When I grow a birch tree next to a transparent block (piston, glass, slab, etc...) the blocks (where the leaves are suppost to grow) get destroyed and dosen't drop anything and gets replaced by the leaves insted of having the leaves growing around them. This seems to be constant, except for glowstone and only works with birch trees.
Steps to recreate:
1. Make a 4-5 high pillar of a solid block.
2. Place a transparent block over the pillar.
3. Plant a birch sappling 2 blocks next to the pillar.
4. Use bonemeal to grow the birch tree. (May take 8-10 bonemeal)