Gloom-shroom

Gloom-shroom is a plant that fires 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 between playing Levels 4-4 and 4-5. It is useful in Last Stand and other swarming levels, like Bobsled Bonanza.

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 brain 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. They are just like a short-ranged Gatling Pea that can attack at three lanes and damage all zombies in that range like the Fume-shroom.

Note that they can hit zombies that are eating Wall-nuts 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 deals 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 by 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, Garlic can be placed in rows one and six to funnel zombies into the Gloom-shroom's line of fire (although this obviously will not work against Gargantuars, Catapult Zombies and Zombonis), while a Spikeweed or 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 Garlic 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. Do not place with Tall-nut because it will not attack.

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 funneling down zombies into two or three lanes with the other lanes being full of Gloom-shrooms. Since all zombies that eat are forced to pass through a narrow bottleneck (formed by the Garlics diverting them to the same lane) while being bunched up together, the Gloom-shrooms are able to dispose them relatively easily. Be mindful, however, that a stray Jack-in-the-Box Zombie can ruin this setup if left to his own devices, as his explosion can take out plants on adjacent lanes as well.

Trivia

 * Gloom-shroom is the most expensive mushroom, even without including the price of the Fume-shroom.
 * Gloom-shroom puffs its cheeks while shooting.
 * Gloom-shroom is the only plant that looks up as opposed to the left, right, or at the screen.
 * Gloom-shroom is the only mushroom upgrade, since Gold Magnet is not considered a mushroom because it does not sleep during the day.
 * Living up to its name, 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 is smiling.
 * Gloom-shroom is one of the two plants having its eyes on its mushroom cap, the other one being the Doom-shroom.
 * Gloom-shroom, Doom-shroom, Fume-shroom, and Ice-shroom are the only mushrooms that frown.
 * Gloom-shroom, Starfruit, Cattail, Cob Cannon, and Threepeater are the only plants that can fire outside the lane they are planted on.
 * Gloom-shroom is ranked number two for firing in the most directions (eight), the first being Cattail (everywhere), and the third being Starfruit (five).
 * Gloom-shroom and Doom-shroom are the only mushrooms that do not have a design on their mushroom cap, possibly because their faces are on the mushroom cap.
 * Gloom-shroom has the shortest range of fire, only one square around itself (not including instant kills such as Chomper).
 * There is a glitch on the Nintendo DS version of Plants vs. Zombies where Gloom-shroom will puff non-stop on zombies even though the puffing animation shows only four puffs at a time. Gloom-shroom will still only deal four puffs worth of damage, even though it puffs continuously. This may be the remaining fumes that did not 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."
 * Gloom-shroom is the only upgrade that degrades its range compared to the non-upgraded version.
 * It is not the only upgrade plant to have a negative side effect compared to the plant it upgraded. The other three plants that do this are Cattail, which replaces the ability to have other plants on it (apart from the Pumpkin and its Imitater form) for the ability to shoot multi-directional spikes, Gold Magnet, which replaces its ability to steal the zombie's metal objects with the ability to grab money, and Cob Cannon, which does not fire on its own.
 * It bears a heavy resemblance to the Tack Shooter from the Bloons Tower Defense series and also resembles a Koffing from Pokémon series.
 * Dandelion in Plants vs. Zombies Online does the same thing, but it has a slower fire rate.
 * Phat Beet in Plants vs. Zombies 2 attacks in a similar manner, but also has a crit system and does less damage normally.