Spikeweed

Spikeweed is a passive attacking plant, dealing normal damage to any zombies that dare to tread on it.

Usage
It costs 100 Sun to plant spikeweed. It deals five attacks for every normal speed zombie that passes over it.

Strategy
Plant Spikeweed in front of Wall-nut, Tall-nut or Pumpkin. Zombies cannot harm it, and are continuously damaged as they try to break down the wall.

Spikeweed is also an excellent counter against Zombonis if no other recourse is available.