Minecraft wiki entry for Traps, associated text: Surround your base with a field of wither roses or sweet berry bushes, and leave a block-wide path leading to your base, or make a hidden underground tunnel leading to it. Any hostile mob that walks through the field takes significant damage, but unless you make the field large enough, this trap isn't fatal. This trap works only on mobs and not on players, because players can disarm it quickly with just a water bucket. For added effect, place cobwebs on top of the plants, and if you are using wither roses, plant them on soul sand. This way, the mobs have to spend more time inside the trap, making it more fatal.