Smash-shroom

Smash-shrooms are a new plant introduced in Project Z. They are unlocked after the fifth level of Deep Dark Woods is beaten.

Ability
Smash-shrooms are single use plants that float above a square until there are at least 4 zombies on it. Once this criteria is met, they slam down and crush the zombies, killing them. Afterwards they disapear.

Strategies
Smash-shrooms are best used in conjunction with any kind of defensive plant, because it means that zombies will stay on the square. One thing that needs to be kept in mind is that using Coffee Beans, which are unlocked in the next world, Smash-shrooms can be utilised during the daytime.

Trivia

 * Smash-shrooms were originally called Iron-shrooms.