Soil Your Plants

Difficulty: Extremely Easy

This achievement can be easily achieved by playing the first four, or maybe three levels in Adventure Mode. Since Peashooter is the only projectile shooter you have at that time, there's no doubt that you will get this easily.

Trivia

 * It might be reference to some Plants vs. Zombies trailers, where it also says Get ready to soil your plants.
 * It is almost impossible not to get this achievement without hacking.
 * This is one of the few achievements that must be done to finish Adventure Mode, the others are Crash of the Titan and Home Lawn Security (or Resolute Homeowner at the DS version).