Minecraft wiki entry for Huge_mushroom, associated text: Huge mushrooms can be grown by applying bone meal to a small red or brown mushroom that is planted on dirt, coarse dirt, grass blocks, rooted dirt or moss blocks with a skylight and block light level of 12 or less, or on podzol, mycelium or nylium at any light level. A 3 block radius around the mushroom must be free of solid blocks, and 7-9 blocks above the mushroom[needs testing]. Extra tall huge mushrooms (up to 13 blocks tall) have a ~5% chance of growing from mushrooms fed with bone meal.