Threepeater

Threepeater shoots peas in three directions: the lane above it, the lane below it and the lane it is planted on. These are a handy middle-to-late game weapon, although it is best not to place them in the top or bottom rows, as they will shoot two Peas rather than their usual three. However, it is a good idea to plant them there after planting them in the middle rows. It is basically a three headed Peashooter and the most expensive non-upgrade plant.

Suburban Almanac Entry
Threepeater

Threepeaters shoot peas in three lanes.

Damage: normal (for each pea)

Range: three lanes

Threepeater likes reading, backgammon, and long periods of immobility in the park. Threepeater e njoys going to shows, particularly modern jazz. "I'm just looking for that special someone," he says. Threepeater's favorite number is 5.

Cost: 325 (200 in Versus Mode, 400 in Heavy Weapon)

Recharge: fast (very slow in Versus Mode)

Strategy
Since it fires down all three lanes whenever it sees anything in any lane, it can potentially hit zombies just as they enter the right side of the screen - well before other plants have noticed them. Its especially useful in conjunction with the Torchwood and in pool levels, since two Threepeaters in the second and fifth rows (both touching the sides of the pool) can cover all six lanes on a pool level. Keep in mind to protect Threepeaters thoroughly, as 325 Sun takes a while to get.

Threepeaters have somewhat inaccurate animations: what you really get is one pea straight ahead from the square above, one from its square and one from the square below. Because of this Threepeaters work better with Torchwood than the animation might suggest: if a Torchwood is planted directly above or below the Threepeater, the pea will be lit immediately when it is shot. Likewise, if a Torchwood is planted in the row above or below a Threepeater but one column ahead of it, the Threepeater's peas will be lit despite apparently not having fully moved into the row and not having gone through the Torchwood.

It, paired with the Cherry Bomb, are helpful weapons for earning the Pool's Closed Achievement, as it can help defend the pool lanes. Two would be recommended to ensure death of zombies.

I, Zombie
Threepeaters are encountered in various I, Zombie levels, including I, Zombie Endless. Like the Starfruit and Magnet-shroom, the Threepeater is one of the few plants capable of affecting other lanes than the one it's planted in. This allows the player to consider other lanes besides the one currently being assaulted. For example: an Imp about to walk down a seemingly undefended lane might still get killed by a Threepeater, wasting Sun. You may like to remove it with a Bungee Zombie. Ironically, this plant, when it appears, tends to be in weak rows that can easily be dealt with via Football Zombie. Overall, it is one of the dangerous threats of the level, the others being Starfruit, Magnet-shroom and Kernel-pult.

Air Raid
On the DS exclusive Mini-game Air Raid, the Threepeater is the upgrade for the Gatling Pea. The Threepeater will continue to shoot at the rate of a Gatling Pea, but now in three directions, for a total of 12 peas. If your Threepeater is not protected by a Pumpkin and it gets hit, it will revert back to the Gatling Pea. Picking up more than one at a time will not give you more hit points, and will still turn into a Gatling Pea after taking damage.

Trivia

 * If you play I, Zombie Endless with a Threepeater at the top or bottom row, the top or bottom head respectively won't move at all as the cardboard cut-out plants will only move if there is a zombie.
 * The Threepeater's three heads bounce at different speeds. The bottom head bounces the slowest, while the middle head has an average speed, and the top head bounces the fastest.
 * Each head also has a different number of leaves on the back; the bottom one has one leaf, the middle one two, and the top one three.
 * But in the iPad version, all three heads have three leaves.
 * The Threepeater, the Starfruit, the Cattail, the Cob Cannon and the Gloom-shroom are the only plants that can fire outside the lane they are planted on.
 * The Threepeater is obtained during a Pool level and thus, it is equal to three Peashooters and one Lily Pad.
 * Threepeater 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 the Ice-shroom, Lily Pad, Potato Mine, Doom-shroom, Tangle Kelp, Jalapeno, Spikeweed, Torchwood, Tall-nut, Cactus and Blover.
 * The Lawn is flat yet the top head could hit the lane on the left and the bottom head could hit the lane on the right even though the heads are above and below the center head.
 * Threepeater is a portmanteau of the words "three", in reference to the number of heads, and "repeater", in reference to the number of peas it shoots.
 * It is possible to beat a Pool level using only Threepeaters and no any aquatic plants.
 * There is a DS achievement called Don't Drink the Water that can be obtained using this strategy.
 * The Threepeater has the smallest heads out of all of the Peashooters.
 * If the player did not purchase the full version of PvZ, the Threepeater cannot be used, but it still can be seen after you get the Squash, which is unusable too.
 * Despite having 3 heads and 6 leaves on all of his heads, his favorite number is 5. Whether this references anything or if it is just a joke is unknown.
 * This may be a reference to Monty Python and the Holy Grail where Arthur tends to replace the number 3 with 5, such as counting "1, 2, 5."
 * Despite being a 3-headed plant, he only has one personality. Split Pea also only has one personality. The Twin Sunflower's personality is unknown.
 * In Versus Mode, its sun cost is 200, like a normal Repeater.
 * The Threepeater and the Starfruit are the only plants that have different cost, and, slower recharge speeds in Versus Mode.
 * It is weird that a Threepeater shoots 3 peas even though there is only a zombie in the middle.