Spikerock

Spikerock is the upgrade of Spikeweed, and is purchased from Crazy Dave's shop for $7500. It is a passive attacking plant, dealing high damage to any zombies that tread on it. It costs 125 Sun to upgrade a Spikeweed to a Spikerock, for a total cost of 225 Sun. It usually deals ten attacks in groups of two (each attack doing one damage) for every normal speed zombie that passes unimpeded over it (exceptions include zombies that come in a group, when one zombie gets on just after the Spikerock fires). Spikerocks will pop tires one up to nine Vehicles (Zombonis and Catapult Zombies) before death, every three vehicles causing one of its large spikes to break off. (When a Gargantuar attacks it, it will have the same effect as when vehicles roll over it, without the Gargantuar dying.) Since the Spikerock attacks from below, it bypasses shields.


 * Note: Spikerock cannot be planted on Lily Pads or in Flower Pots, due to the fact that zombies cannot walk over them, rendering the plant useless.

Suburban Almanac Entry
Spikerock

Spikerock pop multiple tires and damage zombies that walk over it

Must be planted on Spikeweeds

Spikerock just got back from a trip to Europe. He had a great time, met some wonderful people, really broadened his horizons. He never knew they made museums so big, or put so many paintings in them. That was a big surprise for him.

Recharge: very slow

Cost: 125

Strategy
Use the Snow Pea, Winter Melon or Ice-shrooms to slow the zombies, so they spend more time being attacked by the Spikerock. Snow Pea and Spikerock is particularly cost effective, but if Winter Melons are used, all zombies get slowed.

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 Gargantuars. This considerably slows Gargantuars and allows extra time for your other defences to attack, since unlike other zombies, Gargantuars will stop to destroy the Spikerocks.

Trivia

 * Jack-in-the-Box Zombies, Zombonis, Catapult Zombies, Gargantuars and Giga-Gargantuars are the only zombies capable of damaging Spikeweed and Spikerocks.
 * This does not include Bungee Zombies, which can steal them but not hurt them; however, it appears that Bungee Zombies must come down more than once to steal these.
 * Biologically, Spikerock is not actually a plant, since it's a rock.