Spike

Spike is a kind of projectile that is red and pointy which can only be shot by the Cactus and Cattail. Spikes do the damage of a pea and are the only auto-fired projectiles that can shoot down Balloon Zombies. The Cactus shoots spikes at a normal firing rate down its own lane, whereas the Cattail can shoot down the nearest zombie on any lane and shoots two spikes at a time. Spikes are not affected by Torchwoods. Also, the Cattail's spikes travel slower than the Cactus's. Spikeweeds and Spikerocks also have spikes that hurt the zombies stepping on them, and can also pop tires.