Shrub of Thorns

The Shrub of Thorns is a plant from the Witchery mod. These are trapped shrubs, and look identical to normal dead bushes. When an entity walks over this plant, the plant will turn into a four block high cactus, and the block below it will turn into sand. The plant is consumed whenever an entity walks over it. The Shrub of Thorns can only be harvested by breaking the block it is on top of, which can only be dirt, grass, or sand.