Minecraft wiki entry for Mushroom_farming, associated text: First, a room of the height 2 is needed, in this room, place a water stream in the floor, 2 blocks wide. It will transport the mushrooms out of the room. Mushrooms should be planted along the bank of the water, leaving every other block empty. Lastly, pistons are required to be placed facing towards the water stream. They need to be placed beside the blocks, where no mushrooms are planted.