Minecraft wiki entry for Dark_oak, associated text: Growing these trees requires four dark oak saplings arranged in a 2×2 grid; they do not grow if planted individually. Dark oak trees grow at a much faster rate than most other trees. They require a 3×3 column of unobstructed space at least 7 blocks above the sapling to grow (8 blocks including the sapling itself). This column is centered on the northwestern sapling. Additionally, dark oak trees require 5×5 layers without obstruction for the top 3 layers of its final height. No horizontal clearance is needed at the base of the tree (saplings planted in a 2×2 hole 1 block deep still grow).