Defcorn 5

Difficulty: Very hard (Medium in Survival Levels, Extremely easy on Last Stand, Survival: Endless, and Last Stand: Endless)

Defcorn 5 is an achievement unlockable on iPhone, iPad, Android, Nook, PlayStation 3, Xbox 360 and PlayStation Vita versions of Plants vs. Zombies. In order to complete it, the player must have five Cob Cannons in a single level.



Strategy 1
Take the following plants: As five Cob Cannons require 3500 sun, it is suggested you play the first day level, as it contains only normal zombie and it is easy to beat. It's also possible to use this in Survival: Day. Use Garlic in every other lane (one, three, and five) to force the zombies into two rows, placing three Spikeweed behind them to incur damage. This will allow you to build up three rows of unthreatened Sunflowers. Whenever the Cob Cannon charges, you can take out two Sunflowers and plant another Cob Cannon.
 * Spikeweed
 * Garlic
 * Sunflower
 * Kernel-pult
 * Cob Cannon
 * Imitater Sunflower
 * Twin Sunflower

You can easily get this achievement in Last Stand as you start with 5000 sun, enough to plant six Cob Cannons and two Wall-nuts in front of each.

It is not necessary to complete the mini-game to earn the achievement.

Note: If there are Gargantuars in the level, you can also get the achievement Popcorn Party in the process.

Strategy 2
Use the following plants:
 * Peashooters of any kind or Cabbage-pults
 * Kernel-pults
 * Cob Cannons
 * Imitater Sunflowers
 * Twin Sunflowers (Optional, but provides more sun)
 * Wall-nuts or Tall-nuts
 * Pumpkins (Optional, but provides additional protection for your Wall-nuts and Tall-nuts)
 * Any instant kills you want
 * Wall-nut First Aid to avoid having dig up and re-plant Wall-nuts and Tall-nuts

Play the first day level (replaying Adventure Mode). Start out as you normally would, planting Sunflowers on the row closest to the lawn mowers. Upgrade your Sunflowers to Twin Sunflowers throughout the level when you can. Plant Peashooters or Cabbage-pults in the row after your Sunflowers (plant according to which lane the Kernel-pults in the third and fourth rows from the back and plant Wall-nuts or Tall-nuts in the fifth row. Place Kernel-pult the level as you normally would, upgrading your Kernel-pults to Cob Cannons whenever possible.

When you reach the final wave, try to take out all the zombies in every row except one (one that has a Cob Cannon in it). Leave one or two zombies in that lane and immediately remove all Peashooters or Cabbage-pults. Now nothing should be attacking the zombies left in the lane, and they should be noshing away on the Wall-nut or Tall-nut (and Pumpkin, if you have one). It is best to have only one zombie left, as this will reduce the Wall-nut's or Tall-nut's rate of deterioration. Now steadily collect the sun produced by your Sunflowers, occasionally re-planting a Pumpkin or planting a Wall-nut or Tall-nut over the previous one. Upgrade your Kernel-pults to Cob Cannons when you have enough sun, use a Corn Cob Missile to take out the remaining zombies when you have all five Cob Cannons, and then you are done.

Last Stand Strategy
Because 5000 sun is given at the start and only 3500 is needed to plant five Cob Cannons, all you really need to do is plant ten Kernel-pults and then upgrade them to Cob Cannons. You do not even have to start the Onslaught, so you can start a game, build the five Cob Cannons, then leave.

Trivia

 * This achievement is a reference to Defcon, or Defense Readiness Condition, a scale of alert for the U.S. armed forces. Ironically, Defcon 5 is actually the lowest state of emergency, while five Cob Cannons in a normal Adventure Mode level being somewhat of overkill.
 * This is one of the three achievements involving Cob Cannons, the other being Popcorn Party and No-Cob-No-Explode.
 * This is relatively easy to get in Last Stand but gets rid of most of the player's sun, costing 700 for each Cob Cannon (two Kernel-pults and the Upgrade: 200 sun plus 500 sun equals 700 sun).
 * Along with Melon-y Lane, this is an extremely easy achievement because it can be unlocked in Last Stand. Coincidentally, both of them involve upgrade plants that are planted on Lobbed-shot Plants.