Minecraft wiki entry for Pumpkin_and_melon_farming, associated text: For high output per growing space, plant 4 stems (2 pumpkin stems and 2 melon stems) adjacent to the growing space, and surround each stem's root with 6 wet farmlands, so its growth rate is the maximum value (1/3 per random block tick) (1/12 for each available space adjacent to stem). Growing spaces surrounded by 4 such stems have the highest possible output rate per growing space. Potatoes are planted to prevent pumpkin or melon growing on farmland where they they are not wanted. The border of farm surrounding the outer stems should have potatoes on wet farmland too if there is available space. A water block is placed in every 8x8 area. Stems around the water block in the middle of the farm has 5 wet farmland around them, so their growth rate is slightly reduced to 1/4 per random block tick (1/16 for each available space adjacent to the stem). When the farm is extended in the schematic's east-west direction, sharing the leftmost and rightmost redstone dust on the stationary block, 1 pumpkin or melon fruit growing trigger 8 pistons at the same time.