Ice-shroom is a mushroom appearing in Plants vs. Zombies. When activated either through normal planting in Night and Fog levels, or through waking up via Coffee Bean in levels with daylight, Ice-shroom will freeze all enemies currently on the field, dealing 20 damage per shot worth of damage and stunning them for 3.25 seconds. Afterwards, the affected targets will continue to be chilled for another 16 seconds, during which their movement and attack speed are halved.
Airborne enemies will only suffer from the chilling effect while Zomboni, Zombie Bobsled Team, and underground Digger Zombie are immune to Ice-shroom altogether. Attacking with fire-based plants will also immediately remove both the stunning and chilling effect.
Origins
The "ice" in his name refers to the fact that he freezes zombies with ice and the "shroom" in his name refers to the fact that he is a mushroom.
Judging by his color and flat cap, Ice-shroom might be based on the aniseed toadstool (Clitocybe odora), a blue-green mushroom that grows near deciduous and coniferous trees.
Suburban Almanac entry
Ice-shroom
Ice-shrooms temporarily immobilize all zombies on the screen.
Damage: very light, immobilizes zombies
Range: all zombies on the screen
Usage: single use, instant
Sleeps during the day
Ice-shroom frowns, not because he's unhappy or because he disapproves, but because of a childhood injury that left his facial nerves paralyzed.
Cost: 75
Recharge: very slow
Strategies
Ice-shroom is a useful plant that can help the user in delaying the horde and maximizing the plants' efficiency. As he can affect every single enemy on the screen, Ice-shroom will prove to be highly useful in normal levels, as other slowing options are either expensive or limited in scale. Ice-shroom's value, however, suffers greatly in Survival: Endless, as the player is likely going to have enough Winter Melons to suppress the horde, and the stunning duration of only 3.25 seconds is too trivial to have a great impact on the battle.
Unlike most other mushrooms, the nocturnal plant mechanic does not necessarily affect Ice-shroom negatively, as he will not activate immediately when planted in daylight levels. This allows the player to "stockpile" Ice-shrooms by planting them on safe space and activating them when needed. Pumpkins can also be used to guard sleeping Ice-shrooms, giving the player more liberty in storing them for further use.
For Pool and Fog levels, Ice-shroom could be activated in 3 seconds before the disappearance of "a huge wave of zombies is approaching" to prevent zombies rising from the water. This strategy is very important in the Survival: Endless if your unprotected plants are set in the rightmost 8 tiles of the pool. On the Roof, Ice-shroom could also be activated when the bungee zombies begin to drop ambush zombies at the final flag to stun and freeze them. The ambush zombies can be stunned and frozen in midair as well. Giving time for the plants to deal with the zombies.
Ice-shroom is provided at this level as the only method to negate Dr. Zomboss's fireball attack. Therefore, the player should not try to deplete their stock too quickly, and instead, only use Ice-shroom when either a fireball or dangerous enemies are present. Stunning Dr. Zomboss when he lowers his robot can also speed up the level by giving the plants more time to damage him. However, unless there is an iceball present, avoid using Jalapeno when he is frozen, as the fire will take away both the chilling and freezing effect.
As invisible zombies will still have ice formed on their feet when frozen, Ice-shroom can be used to scan the lawn for potential threats. This will not work on pool lanes however.
In Survival: Endless, Ice-shroom will see its value inversely proportional to the amount of Cob Cannons utilized by the player, as the few seconds earned with each Ice-shroom will matter more when less firepower is present to actually fight the horde. Stockpiling Ice-shrooms remains a powerful strategy, and there are three ways the player could do this:
Placing Ice-shroom on the pool row is the safest option since there is much less pressure from the zombies in these lanes. However, the pool is also the best place for installing Cob Cannon and Twin Sunflower for the same reason, therefore, this option will force the player to sacrifice great amounts of firepower.
Placing Ice-shroom on the back columns in normal lanes will expose it to Imps and Digger Zombies, forcing the player to divert further attention to Pumpkin maintenance. This is usually the preferred option, however, since it does not require much firepower sacrifice.
Placing Ice-shroom at the frontline is the most dangerous option, as this will put Ice-shroom in the path of various threats such as Zombonis, Football Zombies, and Gargantuars. This is usually a last-ditch option, but it still has its merits, namely not allowing Imps to attack Ice-shroom and not requiring Pumpkin if the crowd is well controlled.
When used on a Pool or Fog level, the pool's animation stops until the zombies are unfrozen.
Even though his Suburban Almanac entry says that the damage is very light, it is actually the same as damage from one pea, which is stated as normal in Almanac.
If the Ice-shroom gets squashed by an Zomboni, he will instantly explode.
