Create's Tree Fertilizer is like a special type of bonemeal, specific to saplings, that grows a tree on the first click so you don't waste resources. However, when using it on a sapling for a Ritual of the Forest, it can still grow a tall tree. When a tree grows from using Tree Fertilizer, the ritual just ignores it. Spamming bonemeal grows a tree that always triggers the ritual, but the whole point of Tree Fertilizer is to help out when you're low on bone meal in the first place and can't afford to spam it. It would be super handy for automation of ritual items if this could be a sort of "instant complete" thing

Looks like Tree Fertilizer also doesn't work for ancient saplings