Cactus is a block that is usually found in desert but sometimes you can see them on the side of beaches in other biomes. They will grow up to 3 blocks high if there is room above it. For the cactus to placed on the ground it is required to be placed on a sand block. Just like farming the patch will need sunlight to grow. Cactus blocks will do damage to both players and mobs by half a heart of damage every half second. The item will also destroy any items that gets in contact with the cactus. When destroyed it can drop a cactus per each block. If the cactus is three blocks high, destroying the bottom or middle block will destroy the entire patch dropping every piece at once. it is usually used as a fence from mobs and great for the nether since it can not be put on fire. Cactus however can not be placed side by side so they will require one block of space in between them.