Shadow-shroom

Shadow-shroom is the third plant obtained in Modern Day in Plants vs. Zombies 2. It explodes into poison once a zombie eats it, and the poison effect deals 900 damage per shot worth of damage for 30 seconds and ignores all armors, such as buckets and ice blocks. When Shadow-shroom is powered by a Moonflower, the zombie who eats it can also spread the poison effect to nearby zombies.
 * For a similar named plant in Plants vs. Zombies Heroes, see Poison Mushroom.

In the Chinese version, its effect no longer ignores all armors. Instead, it directly damages the zombies' armor.

Plant Food effect
When fed with Plant Food, Shadow-shroom will take a deep breath then cause an ink explosion, poisoning every zombie (except Imp Cannons) on screen. Zombies already poisoned will have the poison effect cured, but receive 45 non-armor piercing damage immediately instead.

Costumed
Its effect now slows down zombies.

Strategies
Shadow-shroom's main role in the player's arsenal is to counter armored enemies by bypassing their armor altogether and damage them directly. While Shadow-shroom's main advantage is its relatively fast recharge rate, it is ultimately not a stellar plant for its job as most other instant use plants of similar recharge rate such as Ghost Pepper and Lava Guava, as they can deal enough damage to render zombie armor not a significant issue. Shadow-shroom also receives a great weakness in its very poor effect radius, which is not addressed at all when powered due to the poison requiring zombies to be close together to spread. In addition, Shadow-shroom's low damage potential and lengthy time required to deal full damage makes it a poor choice against high health enemies without armor, in particular mechanical enemies and Gargantuars.

The player may find great value in Shadow-shroom's Plant Food ability: As it can poison every enemy on the screen, the Plant Food effect will make short work of all armored zombies. Dark Ages and Jurassic Marsh provide prime example of this, as Knight Zombies are frequent sights in the Dark Ages due to Zombie Kings, while the enemy composition in Jurassic Marsh is primarily consisted of armored zombies, meaning only Jurassic Bullies and Jurassic Gargantuars can survive the attack.

A powered Shadow-shroom can benefit from being paired with slowing plants, defensive plants, or speedy zombies. For example, Hurrikale or Chard Guard can knock the poisoned target back into the zombie crowd and spread the effect, while Garlic or Sweet Potato can be used to create choke points for Shadow-shroom to affect more enemies. Shadow-shroom is also a helpful plant for fighting Pharaoh Zombies and Newspaper Zombies, since it can neutralize them without breaking their armor and causing them to accelerate.

Avoid using Shadow-shroom against Jester Zombies while spinning as they're immune to the poison effect. Using Shadow-shroom on hordes of Zombie Chickens or Ice Weasels (unless fed with Plant Food or powered by Moonflower) are also a bad idea as only one Zombie Chicken or Ice Weasel can get poisoned.

Trivia

 * When planting a Shadow-shroom that is not going to be powered by Moonflower, the player can briefly see it powered up.
 * If one investigates how the Shadow-shroom looks carefully, it can be said that it looks slightly like the Pokémon Shellder, due to it having a large tongue that is almost always sticking out and having a large cap that resembles a shell.
 * Recently planted Shadow-shrooms near Moonflowers when eaten by zombies after planting, might not have their boost effect.
 * This is because shadow plants take around half a second to be powered by a Moonflower when planted within said Moonfloower's 3x3 tile radius.
 * If it is planted during Last Stand setup, it appears to be powered, even though the player cannot use Moonflowers.
 * It and level 2 Endurian in the Chinese version of Plants vs. Zombies 2 are the only plants that ignore zombie armor when attacking.
 * This is the only international plant that can do this.
 * If there is a frozen block with a zombie inside on the lawn and the player uses Plant Food on Shadow-shroom, the zombie will be poisoned, but it will not suffer any damage unless the frozen block is destroyed.
 * It is the only shadow plant that is a mushroom.
 * A powered Shadow-shroom is featured on the icon for the achievement The Shadow Family. The Shadow-shroom in the achievement's icon is not poking its tongue out.
 * This is the only time where a Shadow-shroom is seen with its mouth shut.
 * However, in the game, if the player pauses or screenshots at the right time, it may not be sticking out its tongue.
 * It and Toadstool are the only mushrooms known to stick their tongues out.
 * It, Dusk Lobber, and Moonflower are the only shadow plants that emit high-pitched vocal effects when performing their action.

Specific to Chinese version

 * It is the third plant from the international version whose ability was nerfed (which is unable to damage zombies directly, and instead damages their headwear first), the first being Electric Blueberry (which is unable to target zombies in other lane at level 1 (unless upgraded to level 3) and cannot kill zombies with one hit) and the second being Shrinking Violet (which is unable to shrink Gargantuars at level 1).
 * The zombies before Lost City don't have the visual poison mask when they eat it.