Wall-nut

The Wall-nut is the first defensive structure. It lasts approximately 72 normal zombie "chomps" (or about 40 seconds), and changes appearances at 24 chomps and 48 chomps before being swallowed at 72 chomps.

Usage
Place the Wall-nut in front of your other plants to block the zombies.

Suburban Almanac Entry
Wall-nut Wall-nuts have hard shells which you can use to protect your other plants. Toughness: high "People wonder how I feel about getting constantly chewed on by zombies," says Wall-nut. "what they don't realize is that with my limited senses all I can feel is a kind of tingling, like a relaxing back rub."

Cost: 50

Recharge: slow

Standard Levels
Most plants are very vulnerable to being eaten by Zombies, so you need some sort of defense to keep the tougher zombies from chewing through your lines. Wall-nuts are cheap, so they can make a good early defense, especially when combined with a Peashooter or Spikeweed. Later, when you can afford it, you'll want to upgrade with Wall-nut First Aid from Crazy Dave's Twiddydinkies, as this will allow you to replace Wall-nuts that have been damaged without having to dig them up first. When the Wall-nut starts to look sad, it only has a few chomps left, so try to replace them quickly at that point.

Note that Pogo Zombies, Pole Vaulting Zombies, Dolphin Rider Zombies, and Ladder Zombies can easily get past Wall-Nuts, and they will only slow down Gargantuars for as long as it takes for them to smash the Wall-nut.

Wall-nut Bowling and Wall-nut Bowling 2 Mini-games
Wall-nuts are your standard ammo in Wall-nut Bowling. They will take out normal Zombies in one hit, Conehead Zombies and Newspaper Zombies in two, and Buckethead Zombies in three. After striking any zombie, the Wall-nut will bounce off at an angle, possibly hitting more Zombies before it rolls off the screen. Try to hit more than one zombie with each Wall-nut, as each additional zombie yields more coins (0 for the first, 1 for the second, 2 for the third, and so on). Also, remember that the Wall-nut doesn't have to go directly at a Pole Vaulting Zombie to make it jump - it just has to be near enough. There are two Wall-nut variations found in these Mini-games:

Explode-o-nut
The Explode-o-nut is found in Wall-nut Bowling and Wall-nut Bowling 2. It is a red Wall-nut which, upon hitting a zombie, creates an explosion the size of that from a Cherry Bomb.

Giant Wall-nut
The Giant Wall-nut is only found in Wall-nut Bowling 2. When used, it rolls down a row and squashes all the zombies, acting as a sort of Jalapeno.

ZomBotany and ZomBotany 2 Mini-games
The Wall-Nut Zombies in the ZomBotany mini-games are very resistant to damage, taking the same amount of damage as a Football Zombie. The best plan is to stop them with Wall-nuts of your own while hitting them with as much damage as you can. The Wall-nuts also serve to stop Tall-nut Zombies, and the peas of Peashooter and Gatling Pea Zombies.

Beghouled & Beghouled Twist mini-games
It's difficult to control when and where you will get Wall-nuts in this game, so it's almost pointless to upgrade them to Tall-nuts. If you do manage to get three or more on the front, try to leave them there and only complete matches in the rear lanes (especially Wall-nuts in any other column).

Totally Nuts I, Zombie level
Ladder Zombies are pretty much required here unless you luck out and get a lane with no offensive plants at all. Ladder Zombies can survive many hits, so they are generally fine for any lane with only a single regular Peashooter or Fume-shroom in the second or third slot from the left. If there is more than one attacking plant of any kind, you will need to follow the Ladder Zombie up with a Buckethead Zombie, and if there are Snow Peas you may need a second Ladder Zombie. Regular Zombies are almost useless on this level, except to follow a Ladder Zombie when he dies right before eating the Brains.

Portal Combat Mini-game
Use the Wall-nuts you get here to protect particularly vunerable Portals (e.g. ones that lead straight to the back behind all your plants) from the the front or from behind.