I tested to see if this happens with every block. The only blocks that the trees managed to grow through were dirt, grass, and oak tree leaves and wood. The trees were unable to grow through wood planks or cobble, so if you're making a tree farm and trying to limit tree size, use those materials.
Confirmed still in Minecraft version 1.8.
I tested to see if this happens with every block. The only blocks that the trees managed to grow through were dirt, grass, and oak tree leaves and wood. The trees were unable to grow through wood planks or cobble, so if you're making a tree farm and trying to limit tree size, use those materials.