Although Gargantuar is a slow zombie, it is has a high amount of health and can instantly destroy your plants by smashing them. Hypno-shroom, Garlic, Wall-nut, Tall-nut, and Pumpkin are useless against it. Once it is damaged enough, it will throw its Imp. The player must deal with its Imp as well as the Gargantuar. Even if your defense is good on the Gargantuar, if you lack Imp defense, it will eat your plants and walk to your roof cleaners or chimney.
Since no Bungee Zombies will steal your plants, three of them will drop additional ambush zombies instead. A Squash or Cherry Bomb is recommended to prevent them from eating the player's plants.
Plant two columns of Sunflowers on the first and second columns. Plant a Cabbage-pult or Kernel-pult once you see the first regular Zombie.
Plant a column of Cabbage-pults and Kernel-pults on the third and fourth columns. Once you have enough sun, you can plant the Fume-shroom and Coffee Bean. This will damage multiple zombies on your lanes.
When the Gargantuar shows up
It is not advised to use Ice-shrooms and Doom-shrooms with Coffee Beans, because they have very slow recharge. Instead, use a Squash and then a Jalapeno for good defenses.
Only use instant-kills for emergency once the Gargantuar has thrown its Imp. This is a good way to prevent very slow recharging.
Replace the second lane of Sunflowers with Kernel-pults. This will cause more butter to come out and stun the zombies.
When the Bungee Zombies drop ambush zombies, avoid using the Cherry Bomb early. Once too many zombies are close to the empty Flower Pot, use the Cherry Bomb to deal more damage to the Gargantuar and destroy all the other zombies. Then, use the Jalapeno to destroy its Imp.