Iceberg Lettuce

Iceberg Lettuce is a plant in Plants vs. Zombies 2 and in Plants vs. Zombies Online. It is free of sun cost and freezes any zombie that goes near it for ten seconds. It is based on the real life iceberg lettuce, also known as the crisphead. If a frozen zombie is attacked by a fire plant like Snapdragon, the zombie will thaw out and continue to move on.

Almanac entry
Sun cost: 0

AREA: Single RANGE: Touch RECHARGE: Sluggish

Iceberg Lettuces freeze a zombie when stepped on.

Usage: single use, on contact Special: explodes, temporarily freezing a zombie

Don't get lost staring into Iceberg's adorably cute eyes. If you do, it will be your last step... but only if you're a zombie.

Plant Food
When Iceberg Lettuce is given Plant Food, all zombies will be frozen for ten seconds.
 * Bright light bursts from it before freezing zombies.
 * It is similar to the Ice-shroom from Plants vs. Zombies.
 * Iceberg Lettuce will not disappear after this.

Level upgrade
Level 2 

Ranged Attack: Iceberg Lettuce can attack zombies three tiles in front of it. The attack does not slow zombies and can be deflected by Hammer Zombie.

Combat Training: Iceberg Lettuce gains 50% more attack power (150% of initial).

Level 3 

Enhanced Range: Iceberg Lettuce can attack zombies five tiles in front of it, the attack is slightly more powerful.

Cell Activation: Iceberg Lettuce gains another 50% more attack power (200% of initial).

Level 4 

N/A

Costumed
Now when given Plant Food, all zombies will be frozen for ten seconds and some Power Snow snowballs will be thrown to them.

Strategies
Iceberg Lettuce is a basic plant to freeze zombies. Using it to freeze a zombie early on can increase the amount of time to plant Sunflowers. However, unlike other single-use plants or freezing plants, Iceberg Lettuce cannot damage a zombie. This makes it a zombie delayer, rather than a zombie killer. It is also ideal for zombies too tough to kill with the defenses, such as a Buckethead Zombie in a lane with the only attacking plant being a Peashooter. The Plant Food upgrade freezes every zombie and is especially useful during huge waves and when many Wizard Zombies are on the lawn (although if they are off-screen, it can be detrimental due to their long range), but a waste of Plant Food against lone zombies. Pairing it up with another usage of Plant Food on a plant that hits all zombies, such as the Cabbage-pult can damage the zombies, let the defenses weaken the zombies, and kill most of the zombies at once. Iceberg Lettuces can freeze a whole line of Camel Zombies. It is also useful against Explorer Zombies, since when it is stepped on by a Explorer Zombie, the Explorer Zombie not only freezes, but also has its torch burnt out.

In the Chinese version of the game, when leveled up, it shoots projectiles that deal a pea's worth of damage, ableit with upgrades. It is recommended to use these, rather than Puff-shrooms, as they can defeat zombies much quicker. However, if a zombie steps on it, it will still disappear and freeze the zombie.

Its Plant Food upgrade will also greatly help you deal with the Chicken Wrangler Zombies, as it cannot release Zombie Chickens when stunned or frozen. However, do not use it along plants like Snapdragon, Cherry Bomb and Jalapeno, as they can unfreeze the Chicken Wrangler Zombies, allowing it to release Zombie Chickens. Similar to Chicken Wrangler Zombie, Surfer Zombies do not release their surfboards when frozen.

Avoid using Iceberg Lettuce in Frostbite Caves, as it loses its freezing ability; it is only able to slow zombies down.

Trivia

 * Iceberg Lettuce cannot freeze Zombots, but instead slows them down.
 * If a missile from the Zombots hits it, it will disappear and will still slow down the Zombot somehow.
 * If the player uses Plant Food on it, it will freeze every zombie on screen. However, instead of disappearing like Ice-shroom, it will stay on the lawn. It can be a good strategy to protect it and to use Plant Food on it where there are too many zombies but unlike Ice-shroom, when zombies are no longer be frozen, they will move normally.
 * After the 1.9 update, it will not activate when a zombie is frozen or buttered by Kernel-pult, or disabled by E.M.Peach.
 * This makes the Iceberg Lettuce much more useful when attempting to freeze zombies for as long as possible.
 * This is one of the five plants in the series with a sun cost at some point of 0, the other being Puff-shroom, Sea-shroom, Hot Potato, and Tile Turnip on its first planting stage.
 * In Plants vs. Zombies: Official Guide to Protecting Your Brains, the Iceberg Lettuce is referred to as just "Iceberg".
 * While it is using Plant Food, its costume will disappear. This also happens on Snapdragon, Bonk Choy, Spikeweed, and Spikerock.
 * On Spikeweed and Spikerock, the costumes occasionally disappear while simply attacking.
 * It seems to have the same costume as a Peashooter during Christmas.
 * Iceberg Lettuce cannot be burned by lasers fired by Gargantuar Primes.
 * In Plants vs. Zombies Online, Iceberg Lettuce can stop the fireball of the Sphinx.
 * There is a glitch when a zombie has nearly passed over a grave, and the player puts an Iceberg Lettuce right in front of the grave, the plant would try to freeze it but instead it will disappear.
 * The freezing effect of the Iceberg Lettuce can sometimes be useless towards rapidly moving and running zombies, such as Pharaoh Zombie, after destroying its sarcophagus. The plant simply will not catch the zombie and will just disappear.
 * It has offensive capabilities in the Chinese version of Plants vs. Zombies 2.
 * For some reason, Crazy Dave keeps the Iceberg Lettuce in his fridge in the trailer, although in the game the Iceberg Lettuce is fine in all of the levels and places.
 * It may be a reference to its ability to freeze zombies.
 * Placing the Iceberg Lettuce at Gargantuar's back will force it to smash the Iceberg Lettuce but instead of being crushed, it will instead freeze the Gargantuar. Proper timing is required though.
 * If the player manages to freeze 20 zombies at once via its Plant Food upgrade, the player earns the 20 Below Zero achievement.
 * It can stop Jester Zombie from deflecting projectiles.
 * Even though the Iceberg Lettuce cannot affect the water in Big Wave Beach, it will freeze the splash created by a Surfer Zombie when it falls.
 * It also freezes the Surfer Zombie's wave.
 * In Frostbite Caves, it will only slow down zombies, and not freeze them. It is unknown why this happens
 * This could be because the zombies wear warm clothes that protect them from the cold, or they are just adapted to the cold, like in the case of the Ice Weasels, they are zombie animals that are adapted to the cold.
 * Albeit being an ice plant, it can still be frozen in Frostbite Caves, along with Snow Pea and Winter Melon.
 * If an excavator zombie tries to shovel an Iceberg Lettuce, it gets frozen instead.