Overgrass

Overview
Acts like ladders (the one the ladder zombie places) and place-able on plants

Strategy
Put this at the first column over a Split Pea since it costs less than repeater and the zombies cannot eat it also before that block put a defensive plant. Iceberg lettuce or Freezing plants are also useful with the Split pea strategy.

Trivia

 * It is a pun on overpass and grass