Gloom-shroom

The Gloom-shroom shoots fumes in all directions, but with short range, heavily damaging all zombies nearby. It is purchased from Crazy Dave's Twiddydinkies for $7500 and is an upgrade for the Fume-shroom. It is unlocked after Level 4-4. It is useful in Last Stand, and other swarming levels, like Bobsled Bonanza. It's often used along with Garlic.

Suburban Almanac Entry
Gloom-shroom

Gloom-shrooms release heavy fumes in an area around themselves.

Must be planted on fume-shrooms

"I've always enjoyed releasing heavy fumes," says Gloom-shroom. "I know a lot of people aren't cool with that. They say it's rude or that it smells bad. All I can say is, would you rather have your brains eaten by zombies?"

Cost: 150

Recharge: very slow

Overview
The Gloom-shroom causes normal damage with every shot, and while its range is the surrounding patches in all eight directions, the attacking speed is very fast. In fact, it shoots four times in the time that a zombie travels one square of yard. It can take down a Conehead Zombie in an adjacent lane, though it can barely do enough damage to do so by itself. The heavy fumes can even pass through a Screen Door Zombie's screen door just like the Fume-shroom. Note that they can hit zombies that are eating Wall-nut on any of the squares in its range, but not Tall-nuts (unless a Pole Vaulting Zombie, Pogo Zombie, or Dolphin Rider Zombie jumps into it). This plant is essential to surviving any large number of flags in Survival: Endless. It is also a key ingredient in the completion of Wall-Not Attack.

The Gloom-shroom does four damage per second to any given target in its range, which is the same amount of damage a Gatling Pea deals. Its fumes can also hit every single target in its range, like the Fume-shroom, even if they have shields. As before, however, it does not have as much range (short range).

Strategies
One tactic for Pool and Survival: Endless levels is to build a two x three area of Gloom-shrooms in the right-hand side of the pool, all covered by Pumpkins. These will handle pool zombies as well as those in rows two and five. This strategy has the side effect of leaving zombies in rows one and six mostly unscathed, so although these can generally be handled with Cob Cannon shells or consumable plants, such as the Jalapeno, a better idea is to put Gloom-shrooms in the fifth and sixth columns in rows two and five, plus using Fume-shrooms in rows one and six in the fourth and fifth columns. Optionally, Garlics can be placed in rows one and six to funnel zombies into the Gloom-shroom's line of fire (although this obviously won't work against Gargantuars, Catapult Zombies and Zombonis), while a Spikeweed/Spikerock can be placed in rows two and four or five.

Another effective use is a row of Gloom-shrooms in rows two and four or five, with two Garlics at the very end. All land zombies will be moved to rows one and six and be annihilated. Snorkel Zombies and Dolphin Rider Zombies will make it necessary to add a two columns of Pumpkins on Lily Pads in the pool to allow time for the Gloom-shrooms to destroy them. This strategy is perfect for the Mini-game Last Stand, since it can handle all of the zombies encountered. Their effectiveness is hampered by their short range, which makes them vulnerable to Gargantuars when planted on land which will cause them to be smashed.

They can also be used in Survival: Endless (in the column second furthest to the left, on land) in order to dispose of Digger Zombies (and Imps), as there is generally not enough room for Split Pea.

Mini-games
This plant is ideal for Mini-games where the zombies are in very high numbers or have high toughness. Use it for Mini-games like ZomBotany and ZomBotany 2, because Peashooter Zombies and Gatling Pea Zombies could kill your regular plants without being near. It is also recommended for Last Stand, as the huge mobs can overrun other plants. Keep in mind that using three of these in rows two and five costs 1500 Sun (not factoring in Garlics or other plants). A common Gloom-shroom related strategy is called the Gloomwalk, which involves Garlics deterring zombies into two or three lanes, the other lanes being full of Gloom-shrooms.

Trivia

 * The Fume-shroom has a fire range of four spots, but can only do one hit per zombie, per fire. As for Gloom-shroom, it has a fire range of one square (one spot in eight directions), but can do four hits per zombie, per fire, which means the Gloom-shroom was intended for the middle row (or the pool), while the Fume-shroom is meant for protecting one row at a time.
 * The Gloom-shroom is the most expensive mushroom.
 * Gloom-shroom has puffed cheeks while shooting.
 * Fume-shroom was possibly intended for every row, just from a far distance.
 * The gender of this plant is unknown, and Fume-shroom's gender does not help because it is also unknown.
 * The Gloom-shroom is the only plant that looks up as opposed to the left, right, or at the screen.
 * The Gloom-shroom is the only mushroom upgrade, since the Gold Magnet isn't considered a mushroom because it doesn't sleep during the day.
 * Living up to its name, the Gloom-shroom has a constant sad expression; however, despite this, its seed packet in the Suburban Almanac in the PC and Nintendo DS versions show a picture of it like it's smiling.
 * The Gloom-shroom is one of the two plants having its eyes on its mushroom cap, the other one being the Doom-shroom.
 * It is ironic that the Gloom-shroom holds its breath while shooting out fumes, because in its Suburban Almanac entry, it says it doesn't mind the smell. This might be to help it spew out the fumes.
 * The Gloom-shroom, the Doom-shroom, the Fume-shroom, and the Ice-shroom are the only mushrooms that frown.
 * The Gloom-shroom, the Starfruit, the Cattail, the Cob Cannon, and the Threepeater are the only plants that can fire outside the lane they are planted on.
 * The Gloom-shroom and the Doom-shroom are the only mushrooms that don't have a design on their mushroom cap, possibly because their faces are on the mushroom cap.
 * The Gloom-shroom has the shortest range of fire, only one square around itself (not including Instant-kills such as the Chomper).
 * For some reason, the Gloom-shroom knows when to fire its fumes even though its eyes are facing upward.
 * There is a glitch on the Nintendo DS version of Plants vs. Zombies where the Gloom-shroom will puff non-stop on zombies even though the puffing animation shows only four puffs at a time. The Gloom-shroom will still only deal four puffs worth of damage, even though it puffs continuously. This may be the remaining fumes that didn't come all out at the time it fires.
 * Gloom-shroom's name was spelled in its Suburban Almanac entry without the dash between "Gloom" and "Shroom."
 * The Gloom-shroom is ranked number two for firing in the most directions (eight), the first being the Cattail (everywhere), the third being the Starfruit (five).
 * The Gloom-shroom is the only upgrade that degrades its range compared to the non-upgraded version. The Gloom-shroom isn't the only upgrade plant to have a negative side effect compared to the plant it upgraded, however. The other three plants that do this are the Cattail, which replaces the ability to have other plants on it (apart from Pumpkin and Imitater Pumpkin) for the ability to shoot multi-directional spikes, the Gold Magnet, which replaces its ability to steal the zombie's metal objects with the ability to grab money, and the Cob Cannon, which does not fire on its own.