Spikeweed

The Spikeweed is a passive plant that attacks, dealing normal damage to any zombie that walks on it. They can only be planted on the ground (not on Lily Pads or Flower Pots so that makes them useless for Roof levels) and does 5 damage (2 to faster zombies) in the time it takes any normal speed zombie to pass over it. It will also pop the tires of the first Zomboni that drives over. Since the Spikeweed attacks from below, it can bypass shields. Remember that a Zomboni can kill it.

Note: The Spikeweed can't be planted on Lily Pad or Flower Pot. A Spikeweed can be upgraded to Spikerock when planted on ground.

Suburban Almanac Entry
Spikeweed

Spikeweeds pop tires and hurt any zombies that step on them.

Damage: normal

Range: all zombies that walk over it

Special: can't be eaten by zombies

Hockey is Spikeweed's obsession. He's got box seat season tickets. He keeps close track of his favorite players. And he consistently cleans up in the office hockey pool. Just one problem: he's terrified of pucks.

Cost: 100

Recharge: fast

Standard Levels
Plant Spikeweeds in front of Wall-nuts, Tall-nuts or Pumpkins. Most zombies can't harm it, and will be continuously damaged as they try to eat the defensive wall. Spikeweed is especially important for levels with Zombonis, and placing the Spikeweed on the first row will prevent the Zomboni from laying any ice at all (preventing the appearance of the Zombie Bobsled Team). Note that Gargantuars can destroy Spikeweeds in the same way as they can any other plant.

Vasebreaker: Hokey Pokey
Try to lay down either a row of three Spikeweeds or one Spikeweed in front of a Wall-nut to kill the zombies. Timing can be everything, so if you see a Wall-nut, go ahead and break a few vases on the right hand side to see if a Wall-nut will be needed there. If no zombies appear closer than the fourth row from the left, put the Wall-nut on a different row, and lay down Spikeweed instead. Buckethead Zombies are the exception to this, as you can't kill them with just Spikeweed - make sure to have a Wall-nut in place or use a Squash to kill them.

Trivia

 * Somehow, Spikeweeds and Spikerocks damage helmets from headwear zombies, despite them hitting their feet.
 * Even though Spikeweeds can't be planted in Flower Pots during roof levels, Spikeweeds are always in Flower Pots in the Zen Garden.
 * This is probably because a Spikeweed would be useless in a Flower Pot, as zombies wouldn't walk over it, but they don't need to attack any zombies in the Zen Garden.
 * The Spikeweed is actually too wide for its Flower Pot, and sticks out over the sides, like an armed Potato Mine.
 * Spikeweeds and Spikerocks have a faster attack rate than other plants.
 * This is because they attack directly to the zombies.
 * When a Spikeweed is planted in one of the two bottom right squares on Pool and Fog Levels, it will be higher up than other Spikeweeds. This is so you can see them over the level progress bar.
 * The Jack-in-the-Box Zombie, the Zomboni, the Catapult Zombie, the Bungee Zombie, the Gargantuar and the Giga-Gargantuar are the only zombies that can destroy Spikeweeds and Spikerocks.
 * Alone, it takes two Spikeweeds to destroy the regular Zombie.
 * When a Zomboni hits a Spikeweed and then a Squash tries to squash it, the Zomboni will not explode when the Squash squashes it.
 * That's because the Zomboni is already killed after hitting the Spikeweed, so the Squash won't affect it.
 * It is unknown how the Spikeweed can make the Zomboni's ice machine or the Catapult Zombie's catapult machine explode by just popping the tires.
 * Maybe Spikeweed will degrade their health to 0.
 * Spikeweed is one of the twelve plants that appear in the seed selection screen after you get the Grave Buster on the online version, the others are: Ice-shroom, Lily Pad, Potato Mine, Threepeater, Tangle Kelp, Jalapeno, Doom-shroom, Torchwood, Tall-nut, Cactus and Blover.
 * The Spikeweed's flavor text about hockey seems to be in line with its role of destroying Zombonis (a vehicle with a close link to hockey itself) and its main role in the Vasebreaker level Hokey Pokey.
 * If you look closely, its eye pupils are red.
 * The Spikeweed and the Spikerock are the only multi-use plants that can't be eaten.
 * Spikeweed can't be planted on Lily Pads and Flower Pots.
 * Maybe because they won't affect zombies there.
 * But oddly, Spikeweed can be planted on a Flower Pot, not Lily Pads.
 * The Spikeweed, Spikerock, Fume-shroom and Gloom-shroom are the only plants that attack every zombie within it's attack range with same damage to each.
 * It is unknown why Spikeweed, a plant, upgrades into Spikerock, a rock.
 * It is unknown why in I, Zombie, Crazy Dave made a cardboard Spikeweed when it can't be eaten by zombies.
 * Maybe because it can be destroyed or stolen.
 * The color of Spikeweed's plant is looks like mud.