Spikerock

Spikerock is a passive attacking plant, dealing high damage to any zombies that dare to tread on it. It is the upgrade of Spikeweed, and is purchased from Crazy Dave's shop for $7500.

Usage
It costs 125 Sun to upgrade Spikeweed to Spikerock, for a total cost of 225 Sun. It deals five attacks (each doing 2 damage) for every normal speed zombie that passes unimpeded over it. It deals group damage to ALL zombies that stand on it at any given time.

Strategy
Slow zombies so they spend more time being attacked by the Spikerock, using the Snow Pea, Winter Melon or Ice-shroom. Snow Pea and Spikerock is particularly cost effective.

Plant Spikerock in front of Wall-nut, Tall-nut, or Pumpkin. Most zombies do not attack it, and are continuously damaged as they try to break down the wall.

The Spikerock is (uniquely) capable of withstanding multiple strikes from Gargantuar. This considerably slows Gargantuar and allows extra time for your other defences to attack.

Spikerocks will pop tires on three vehicles (Zombonis and Catapult Zombies), which instantly kills them. Spikeweed only lasts for one.

Jack-in-the-Box Zombies, Zombonis, Catapult Zombies and Gargantuars are the only zombies capable of damaging Spikeweed and Spikerock.