I tried my world in single player and on a server. Optimized from 1.15.2 to 20w18a. For me, it seems dark oak saplings will grow with bonemeal when they are exposed directly to the sky. I have a tree farm underground, and those trees have stopped growing altogether and will not grow even after using a full stack of bonemeal on 1 sapling. When taking the same saplings from my underground farm up top into my plains biome right above my base, the saplings will grow when bonemeal is applied. Still an issue for the underground base.
Jon Whisman
I tried my world in single player and on a server. Optimized from 1.15.2 to 20w18a. For me, it seems dark oak saplings will grow with bonemeal when they are exposed directly to the sky. I have a tree farm underground, and those trees have stopped growing altogether and will not grow even after using a full stack of bonemeal on 1 sapling. When taking the same saplings from my underground farm up top into my plains biome right above my base, the saplings will grow when bonemeal is applied. Still an issue for the underground base.