- Snorkel zombies - Use walnut on lily pad.
- Digger zombies - can't pass through potatoe mines. Use pumpkin to protect all plants in case digger zombies managed to pass through the front defense.
- Zomboni is effectively dealt with using spikeweed.
- Gargantuar is most effectively dealt with using freezing techniques; freezing melon or freeze shroom(use multiple to freeze them so that shooting pea at the left side can shoot them while they are immobilized). Secondly effective using spikeweed (which will slow them down while they are trying to demolish the spikeweed).
The maximum number of flags I have achieved is 22 flags.
Also refer to