The strategy for this achievement is easier said than done. To earn it, it is suggested that you save all your instants, like Squash, for emergencies such as Ladder Zombies, Jack-in-the-Box Zombies, and Gargantuars. Of course, never use the Jalapeno. When you receive Pumpkins, use them to protect Magnet-shrooms and Melon-pults.
Plant the Tall-nuts in column seven (column one being the one closest to your chimney) then put the Magnet-shrooms right behind them with a Pumpkin if available (note: save the Potato Mines but you can put them in column one as a last defense) then fill columns two to four with Melon-pults leaving column five for Chompers if you get them (if your at the second flag and you don't have a Chomper fill the space with a Melon-pult). Try to save at least one Flower Pot to place in front of the Tall-nuts in column eight to plant Squashes to kill the Gargantuars.
While not impossible, it is extremely difficult to complete this achievement without at least three rows of Melon-pults. A constant supply of Pumpkins and Squash may help.
A pretty luck based strategy is to put four to five Melon-pults at the back, Magnet-shrooms in front and then Tall-nuts. You can also put some Squashes or Chompers behind the Magnet-shrooms, if it comes to a time where it looks impossible either let them hit Roof Cleaners or if you have some plant a defensive plant.