Tip:Using the traditional strategy for Powder Keg levels to beat this level!
Start with planting your sun-producer plants at the second column.
Defeat the first zombies with Potato Mines. Meanwhile, if you see a Torch Kongfu Zombie, put an Iceberg Lettuce at the first column in the row that it's in, in order to freeze the fire when it almost reaches the keg, so the zombies can only burn it again when they have broken your defenses.
After having an Iceberg Lettuce in every row at the back, pretend like this is a normal level. Use your attack plants to attack the zombies, but don't use straight-shot attacking plants as Hammer Zombies will deflect the attack. Use defensive plants and Plant Food if needed.