Snow Pea

The Snow Pea is the second regluar offensive plant that you get in the game which is not an instant kill. It is also one of the three plants that can slow down zombies by freezing them. It does the same amount of damage as the Peashooter, but has a slowing effect to zombies upon contact, making it a valuable asset in your arsenal of plants. It can kill a Conehead Zombie in about 5 squares, so it's about as effective as a Repeater.

Suburban Almanac Entry
Snow Pea

Snow Peas shoot frozen peas that damage and slow the enemy.

Damage: normal, slows zombies

Folks often tell Snow Pea how "cool" he is, or exhort him to "chill out." They tell him to "stay frosty." Snow Pea just rolls his eyes. He's heard 'em all.

Cost: 175 (150 in Versus Mode)

Recharge: fast

Usage
Plant Snow Peas anywhere you would plant Peashooters. They have the same damage and rate of fire as a Peashooter, but since they slow zombies down, they do more damage to a zombie. Slowed zombies move and eat about half as fast as regular zombies of their type. It can also slow down all zombies but cannot slow down the Screen Door Zombie, Ladder Zombie, (unless the screen door or ladder is destroyed, and the Zomboni. The slowing effect lasts for a while even after the Snow Pea has been eaten.

Standard Levels
A single column of Snow Peas will slow down the incoming horde of zombies. Multiple Snow Peas in a single lane don't perform much better, not providing additional slowing effects, so unless you're getting them for free, there's probably no need to plant more than one per lane as they are useless and cost more Sun. Of course, having multiple is helpful when zombies eat one, as they will remain slowed. On the roof levels, Snow Peas cannot shoot over the roof's edge unless they are in the first sloped column, so they are not too helpful. Snow Peas and Kernel-pults work well in conjunction with Wall-nuts/Tall-nuts and Spikeweed/Spikerock. Slowing the zombies down will allow more time for the spikes to do damage to the zombies.

Note that if a frozen pea passes through the flame of a Torchwood, it will thaw into a regular pea. Furthermore a slowed zombie hit with a flaming pea will thaw, so it is generally unwise to use Snow Peas in the same lanes as Torchwoods. But if two Torchwoods are placed in the same row where a Snow Pea is planted, the frozen pea will turn into a flaming pea. Also, Screen Door Zombies are immune to the Snow Pea's slowing effect as long as they still have their screen door; the same applies with all shield zombies.

If you still wish to use a Snow Pea with a Torchwood, you could place the Snow Pea in front of the Torchwood. However, the normal flaming peas will still thaw its target, making it relatively useless in this situation. Also, once Winter Melons become available, it may be a good idea to replace Snow Peas in favor of the damage and splash slowing effect; it is also a good combination with the Kernel-pult.

Slot Machine Mini-game
You can't really control when you get Snow Peas, but try to spread them out, one per lane, until you have at least one in each lane. It depends on your luck when you get them or not.

I, Zombie Endless
These are among your worst enemies. You can put down Ladder Zombies to negate the freezing effect, but look out for Magnet-shrooms and Fume-shrooms. They get very annoying.

Trivia

 * Its name is a reference to the snow pea, a pea that grows at the end of winter.
 * This is one of the three Plants that have ice crystals (that replaces its leaves) and freeze Zombies that approach Your House, the other two being the Ice-shroom and the Winter Melon, however the Ice-shroom completely leaves all the zombies frozen in place.
 * All three of these freezing plants will cause a killed zombie to fall over at a slower rate.
 * Also, the Ice-shroom technically doesn't have leaves.
 * Snow Peas are effectively the same as a Repeater, because they do the same amount of damage for the same length the zombie walks. However, the Snow Pea cannot be stacked on a single lane, as the freezing affects only the first zombie in the row, but has more synergy with other plants than a Repeater (though the Torchwood has even more synergy than a Snow Pea and destroys the Snow Pea's synergy).
 * If there is a Peashooter (or a Repeater, Threepeater, etc.) shooting in the same row with a Torchwood before the Snow Pea (the Peashooter using the Torchwood and the Snow Pea put in front of the Torchwood), the flaming pea will cancel the effect of the Snow Pea or vice-versa, so it is not advisable to put a Peashooter with a Torchwood on the same lane as the Snow Pea. If the Torchwood is in front of the Snow Pea, the frozen pea will become unfrozen.
 * In the cover art for the Plants vs. Zombies Original Soundtrack, the Snow Pea uses its mouth as a trumpet.
 * If a pea-shooting ZomBotany Zombie is frozen, it will be slowed down, but it still fires peas at the same rate.
 * When the Snow Pea shoots a frozen pea, a small glittering sound is heard (except in DS/DSiWare version, where the sound will be louder).
 * Snow Pea's sun in Versus Mode is 150, similar to Repeater and Cherry Bomb.
 * An Imitater Snow Pea looks like it's made out of salt.
 * It cannot affect shield zombies with their shield.
 * There's a glitch that might occur if a Pole Vaulting Zombie vaults over a Torchwood into a Snow Pea; the frozen peas shot by the Snow Pea while it is getting eaten will go through the Pole Vaulting Zombie into the Torchwood without freezing or damaging the Pole Vaulter.
 * In the DS/DSiWare versions, its frozen peas look like snowballs.
 * It is the only plant in the peashooting family that has a different color.
 * According to the almanac, Snow Pea is a male.