Minecraft wiki entry for Azalea, associated text: Unlike saplings, an azalea or a flowering azalea does not automatically grow into an azalea tree. Therefore, using bone meal on it is the only way to grow an azalea tree. Application of bone meal gives an azalea or flowering azalea a 45% chance to grow into an azalea tree, provided there is a 3×5×3 area above it that is clear of all blocks that are not leaves or logs.