Grounded is an achivement in Plants vs. Zombies where you have to complete a normal roof level without using any catapult plants (Melon Pult, Kernel pult or Cabbage pult). They are a couple strategys to do this but one of the best is to use peashooters on the first slope down and put lots of pumpkins on them, you can also add 2 rows of peashooters but this is not reccomended.