The Peashooter is the first plant that you can build. It is the only plant that you can build the first time you play Level 1-1 (the first tutorial level).
The design for the Peashooter appears to be loosely based on the Codonopsis pilosula[1], a type of bellflower.
Usage
The Peashooter shoots peas at what is considered a "normal" rate (approx. one pea every 1.4 seconds). It can decapitate a basic zombie in ten shots.
Strategy
Especially in the earliest levels, before you unlock the Repeater, the Peashooter is going to be the stock standard firepower in your floral arsenal.