Currently, the tree activation logic checks for the vanilla bonemeal item, applying a growth signal to the tree. Equally, there's also the growth effect which is hardcoded to activate when Create's tree fertiliser is applied.

Both of these should instead rely on item tags instead so they are easily expandable to any mod.

Proposed tag names:

• dynamictrees:fertilizer, for bone meal effect
• dynamictrees:enhanced_fertilizer, for growth substance effect