There is a mechanic in game in which if player bone meals a oak or birch saplings while having a flower within the 2 block radius of mentioned saplings or vice versa there is a 5% chance that a bee nest will be spawned alongwith respective trees attached to it. I bone mealed more than 40 saplings while it should have appeared once in 20 or 30 saplings it didn't even spawned even when more than 40 saplings were bone mealed.