Fog is the fourth set of ten levels. It takes place in a fog-covered back garden, so both aquatic plants (or lily pads) and fog-clearing plants are essential. It is also nighttime, so mushrooms become useful once again.
Plants:
| Plant | Cost | Effect | Unlocked |
| Sea-Shroom | 0 | Aquatic, shoots spores at zombies up to three squares away | 4-1 |
| Plantern | 25 | Clears fog in a 10x10 area | 4-1 |
| Cactus | 25 | Can pop balloons in addition to dealing regular damage | 4-1 |
| Blover | 25 | Blows away balloon zombies and fog (temporarily) | 4-1 |
| Split-Pea | 25 | Fires two peas backwards and one pea forwards | 4-1 |
| Starfruit | 25 | Shoots stars in five directions (left, up, down, top right, bottom right) | 4-1 |
| Pumpkin |
25 | Shield that can be planted on top of other plants. | 4-1 |
| Magnet-Shroom | 25 | Attracts all zombies wearing metal items in 3-tile radius | 4-1 |
| Cabbage-Pult White | 25 | Lobs cabbages to deal twice the damage of the pea-shooter, but with half the firing rate. | 4-1 |
