Plantern

The Plantern will illuminate a small area of fog, allowing you to see the approaching zombies. Plant it within the foggy area on the right side of the screen to push back the fog, revealing the enemy. If Planterns are planted one square into the foggy area in the rows on either side of the pool, all of the fog will disappear aside from some scraps of it in the corners of the screen. They can be planted anywhere, but are useless except for in Fog and Vasebreaker levels. Technically, like the Grave Buster, the Plantern is not actually a Night plant, because it is not a Mushroom, and therefore it does not need to be placed in the Night Environment in your Zen Garden.

Suburban Almanac Entry
Plantern

Planterns light up an area, letting you see through fog.

Range: one lane

Special: Lets you see through fog

Plantern defies science. He just does. Other plants eat light and excrete oxygen; Plantern eats darkness and excretes light. Plantern's cagey about how he does it. "I'm not gonna say 'sorcery,' I wouldn't use the term 'dark forces,' I just... I think I've said enough."

Cost: 25

Recharge: slow

Standard Levels
It is a good idea to put Planterns behind defensive plants such as Wall-nuts or Garlic to keep them from being eaten, or inside a Pumpkin if you can. You should plant only two Planterns in a level, place it near the pool on the fourth row to the right side of the lawn. Note that Planterns are ONLY useful in the Fog levels (Levels 4-1 to 4-9) but cannot be used in level 4-10 (and will not be available) as there is only rain.

Vasebreaker
The Plantern will reveal the contents of any adjacent or diagonally-adjacent vases - up to eight at most. In an emergency, a Plantern may be used as a poor-man's blockade to briefly delay zombies while attempting to kill them with other plants. Ideally. it should be placed in the middle of as many vases as possible.

It's Raining Seeds Mini-game
In the Mini-game It's Raining Seeds, there is fog, so use Planterns the same way that you do in the Adventure Mode levels. However, it depends whether you will recieve the slot packet or not.

Survival: Fog and Survival: Fog (Hard)
In Survival: Fog and Survival: Fog (Hard), use Planterns in the usual way. It is recommended that they are planted during the first two flags (before you get to choose new seed packets). Alternatively, for the Survival levels, you can use Blovers instead, which also gets rid of Balloon Zombies, and makes room for more plants. The Torchwood is also a viable replacement for Planterns as it doubles the firepower of all Pea-shooting plants in addition to clearing fog, but it clears a much smaller area of fog than a Plantern. It is suggested to use a Pumpkin around it to prevent zombies from eating it easily.

Trivia

 * The Plantern is the only plant besides the Torchwood and the Sea-shroom that has visible roots.