Minecraft wiki entry for Cactus_farming, associated text: Generally speaking, the use of pistons in a cactus farm is a very laggy and noncompact way of harvesting. However, in a manual design, the use of pistons can be beneficial as they allow the cactus to be more tightly packed and make it easier to harvest without being damaged. Additionally, since all the cactus are broken at once, there is less for broken cactus to be destroyed.