06/21/12 - Hi Angela! To get the weed killer it takes a couple of steps: First step: Kill the flower on the left side of the stage, then build the LEGO bricks from it into a purple sprinkler. Second step: Have Robin jump into the pool and fill the tank on his Hazard Suit. When it's filled, go to the top right part of the stage and clean up the green goo by the shed. Third step: Now that all the green goo is cleared out, have Batman rip the doors off of the shed. Some bricks fall out. Build these into a lawnmower. The lawnmower cuts down the vines on a silver valve. Run over to the silver valve and turn it, this releases some weed killer from the purple sprinkler that was built earlier. Hope this helps! IA