What plant explodes when a zombie steps on it?

The plant that explodes when a zombie steps on it is the Potato Mine.

Potato Mine is a low-cost defensive plant that must be planted and armed before it can detonate. Once ready, it remains hidden beneath the ground until a zombie steps on it. The explosion destroys the triggering zombie and can damage nearby zombies, making the plant useful for stopping an early group at a fraction of the cost of many offensive plants.

Its delayed activation is central to the design. A freshly planted Potato Mine cannot immediately protect a lane, so players must anticipate where a zombie will arrive and plant it early enough to finish arming. This timing also distinguishes it from Cherry Bomb, which detonates immediately when planted and damages a larger area, and Jalapeno, which clears an entire lane instantly.

The Potato Mine is available among the early daytime plants in Adventure Mode. It is especially effective against ordinary zombies, but it is not a universal solution: tougher enemies may survive or require additional damage depending on the game version and circumstances. The name can also cause confusion with real-world land mines, but in the game it is deliberately presented as a whimsical potato-shaped trap.