Puff-shroom

The Puff-shroom is the first mushroom you get, and although it has an incredibly short range, it's free - a good trade-off, since Sun is much harder to come by at Night. They are nearly as effective as Peashooters, but only have a 3-column shooting range. Of course, as a mushroom, they are only awake at night, and their short range makes the expense of waking them up with a Coffee Bean a waste of sun. They also have a fast recharge, so you can plant two of them in 15 seconds for no cost. They are also too small to be shot by a Peashooter Zombie and a Gatling Pea Zombie.

Suburban Almanac Entry
Puff-shroom 

Puff-shrooms are cheap, but can only fire a short distance.

Damage: normal

Range: short

Sleeps during the day

"I only recently became aware of the existence of zombies," says Puff-shroom. "Like many fungi, I'd just assumed they were fairy tales or movie monsters. This whole experience has been a huge eye-opener for me."

Cost: 0

Recharge: fast

Strategy
Because of their short range, they can only handle basic Zombies, unless used in multiple columns, so more effective plants should be added to your defenses mid-level. Another strategy is to fill the stage from column four over and replace the back ones when you can. These plants can also be used to slow Gargantuars and Giga-gargantuars in Survival: Endless, due to the free cost allowing players to sacrifice them to force the Gargantuars to stop and smash them. Puff-shrooms work well in conjunction with defensive plants as the Puff-shroom has plenty of time to fire at the zombies before getting eaten. These may also be helpful in ZomBotany and ZomBotany 2, as they are too short for the zombies to hit them with peas, making them a good choice for both attacking and stopping Squash Zombies. However, they need Coffee Beans for them to be waken up.

One of the most well-balanced defenses for the Night levels uses two columns of Puff-shrooms (in columns 3 and 4 from the right, although a third can be added in column 2 or 5) behind which one or two columns of Fume-shooms are planted. Behind these are planted two rows of Scaredy-shrooms for long range attacking, with a row of Sun-shrooms to produce sun. They can also be used to stop the Pole Vaulting Zombies that come in the early game in the Night levels when replaying Adventure Mode, but unless you have three columns of them, they still have a chance to get by your Puff-shrooms. What Puff-shrooms lacks in range he makes up for in both cost of sun and numbers.

Note: Puff-shrooms can have problems with even regular zombies, and may get eaten due to several zombies attacking in rapid succession.

Photosensitive
In order to gain the DS achievement Photosensitive (beat a Night level without collecting any Sun), Puff-shrooms are extremely important. The rest of the selected plants are not important, since you can't plant them. (Wall-nuts, Potato Mines and Scaredy-shrooms can be used, but you can only plant either one Wall-nut or two of the others.) The easiest level to achieve this is on Level 2-1, as the only zombies that appear are the regular Zombie and the Newspaper Zombie. Simply plant 3 to 4 columns of Puff-shrooms at the back of the lawn (do not plant Sunflowers, as you may be tempted to collect Sun, therefore failing this achievement). Due to their free Sun cost, do not worry if the zombies eat your Puff-shrooms. Continue to plant and replace your Puff-shrooms, and you should easily achieve Photosensitive.

Trivia

 * Badge-edit-2.png Puff-shroom, Sun-shroom, Spikeweed, Spikerock, Lily Pad and Potato Mine are the only plants that can avoid the peas of the Peashooter Zombie and the Gatling Pea Zombie.
 * However, if they are planted on Flower Pots, the Puff-shroom can be hit by the Peashooter Zombies' and Gatling Pea Zombies' Peas due to the added height of the Flower Pot.
 * This does not happen if you plant it on a Lily Pad.
 * Maybe because the Lily Pad is flatter than a Flower Pot.
 * The Puff-shroom has a 3 square range, since it's just enough to kill a normal Zombie.
 * The Puff-shroom, the Sea-shroom and their Imitater forms are the only plants in the game that cost no Sun.
 * A Puff-shroom is too small for a Pumpkin, but when it shoots a spore, the spore passes through the Pumpkin's shell and still damages the Zombies.
 * This is probably because the Pumpkin has holes in it.
 * The Puff-shroom is the smallest plant in the game, apart from the Potato Mine when it is unarmed.
 * The Puff-shroom, the Sun-shroom, the Spikeweed and the Spikerock are the only plants which, when planted, may not be in the center of a square on the Lawn. They may get planted slightly to the left, right or up.
 * The Puff-shroom, the Fume-shroom, the Gloom-shroom and the Sea-shroom are the only short-ranged shooters.
 * The Puff-shroom and the Sea-shroom are the only shooters with a 3-column range.
 * The Puff-shroom is one of the two cheapest plants in Versus Mode, requiring only 25 sun for the cost of the Coffee Bean. The other is the Potato Mine.
 * Even if the Puff-shroom is at the edge of the red line in Versus Mode, it cannot shoot the Target Zombies, as the distance is just slightly over three squares long.
 * The only time it can shoot the Target Zombie, however, is if its Spore goes past a dead zombie about to fall down.
 * It's weird that the sprout (in Zen Garden) turns into a Puff-shroom even though it does not have any roots.
 * On the iPad version the spore range increases to 4 squares.
 * Crazy Dave mentions that you're kind of lucky to have the Puff-shroom before Level 2-1.
 * This may be because the Puff-shroom costs no sun and you don't get much sun in nighttime levels.
 * You can survive Level 2-1, 2-2, 2-3 and 2-8 with nothing but Puff-shrooms.
 * It is difficult to complete a night level without it, even with Sun-shrooms.
 * You can't use them in No Fungus Among Us, which is why it is so difficult.
 * On the DS and online version if a Puff-shroom shoots an already dead Zombie (after falling), the spore will pass through the entire Lawn.
 * The Puff-shroom, the Sea-shroom and the Scaredy-shroom are the only Plants that shoot Spores.
 * You will receive a warning if you do not choose Puff-shrooms on the first night level.
 * The warning will say "This Level will be extremely difficult without Puff-shrooms. Are you sure you wish to continue without them?"
 * The Puff-shroom, the Twin Sunflower, the Sunflower, the Sun-shroom and the Sea-shroom are the only plants not allowed to be used in Last Stand and Last Stand (iOS Puzzle Mode).
 * You need three of them to kill a Conehead Zombie.
 * When a Puff-shroom shoots a Spore, it looks like he sneezes.
 * A Puff-shroom is a great way to keep Zombies busy while you are planting Sunflowers in a daytime level, because it's free (you don't need to wake them up).
 * Puff shroom is the non-aquatic form of the Sea-shroom, except for the recharge time.
 * Puff-shroom, Peashooter, Wall-nut and Jalapeno are the only plants referenced to in another plant's Suburban Almanac entry.