Plantera

Plantera is a Hardmode boss that can be fought in the Underground Jungle after all three mechanical bosses (The Destroyer, Skeletron Prime, and The Twins) have been defeated. Plantera drops a Temple Key upon defeat, allowing access to the Jungle Temple.

Summoning
After all three mechanical bosses have been defeated, Plantera's Bulbs will randomly spawn in the Underground Jungle (indicated by the status message ""). Destroying one of these bulbs will immediately cause Plantera to spawn, usually a fair distance off-screen. The bulbs will only break if mined with a pickaxe or drill, if they come into contact with lava, or if the Jungle grass underneath them is removed, e.g. via biome spread, actuating the blocks, or the Clentaminator.

Behavior
Plantera moves through blocks slowly, using long vines to grapple foreground blocks, similar to multi-hooks. In the second phase Plantera also grabs background walls. The ends of her vines,, are invincible and deal contact damage.

First form
Plantera creeps after the player, deals damage on contact, and fires the projectiles listed in the following table at them. She generally keeps distance from the player, focusing on her ranged attacks.

Seeds and Poison Seeds are similar to the stingers of Hornets and Queen Bee, and the petals of the Flower Pow. On the, the green Poison Seeds have a /  chance to inflict the Poisoned debuff. Thorn Balls are similar to the projectiles released by Spiky Ball Traps, bouncing around erratically. They can overwhelm the player if they stay in the same area for too long.

Poison Seeds and Thorn Balls are only dispensed while Plantera is below 80% health (0 / / ).

There is a short cooldown after a projectile has been fired, which depends on Plantera's health as well as the type of the projectile:

Second form
Once Plantera is brought down to half of her maximum health (0 / / ), she changes to her second form: her pink petals fall away to reveal a thorn-filled mouth. In this form, Plantera ceases to fire the projectiles from before and instead moves more aggressively in attempts to make contact. Her contact damage is greater than in the first form, but her defense decreases significantly to 10.

Upon transformation, Plantera sprouts eight additional mouths,, that are attached via vines to her body. These deal contact damage and get in the way of the player's attacks, but have comparatively little health. Defeated tentacles will not regrow, making Plantera much easier to fight once all are killed.

Plantera now occasionally releases floating pink spore projectiles that drift towards the player, similar to the spores released by the Giant Fungi Bulb. They can be destroyed in a single hit with any weapon or tool, but travel through blocks and deal high damage. Similarly to the first phase, the cooldown between releases depends on Plantera's health:

Enraged behavior
Plantera becomes "enraged" if she follows the player out of the Underground Jungle, whether it be to the surface, to the Underworld, to a Corrupted/Crimsoned or Hallowed part of the Underground Jungle, or to a completely different biome. This causes her to obtain double damage, double defense (quadruple defense in the second form) and increased movement speed, as well as changing her attack patterns and directly rushing the player. Her projectiles also deal double damage and have reduced cooldowns. Plantera's behavior returns to normal upon re-entry of the Underground Jungle biome.

Expert Mode
In, there are a few significant differences in Plantera's attacks, aside from the default increased health and damage.

In the first form, her pink Seeds can travel through blocks, and all projectiles have limited homing capabilities. The cooldowns are also decreased:

In her second form, Plantera and Plantera's Tentacles move faster than normal. In addition, there are nine more Plantera's Tentacles, attached to Plantera's Hooks in groups of three. Furthermore, the eight tentacles that are attached to Plantera's body can respawn after they have been killed (this does not apply to the tentacles on the hooks). The rate is randomized, but it depends on the number of tentacles that are alive – if all are dead, a new tentacle will be spawned after 5 seconds, on average. This is increased by 5 seconds per living tentacle, hence it takes an average of 180 seconds for all eight tentacles to fully respawn. A single defeated tentacle will take 40 seconds to respawn, on average, assuming the other seven tentacles remain alive for the duration.

Aftermath
Plantera always drops a Temple Key, which grants access to the Jungle Temple and the Golem boss. In the, Temple Keys can also be combined with Biome Key Molds to craft Biome Keys; but in the , Biome Keys drop in their respective biomes and do not require molds.

A status message saying "" will appear upon Plantera's defeat, signaling that new, more difficult enemy types will begin spawning in the Dungeon (see details). These drop powerful new weapons, accessories, and other items. Dungeon Spirits will begin to appear when Dungeon enemies with more than 100 health are slain, which drop Ectoplasm, a new crafting material that offers access to the Pumpkin Moon and Frost Moon events, as well as.

Additionally:
 * The spread of the Corruption, Crimson, and Hallow is halved from their original speed.
 * Biome Keys can now be used to open Biome Chests in the Dungeon (they can unlock Chests pre-Plantera on ).
 * The Cyborg NPC becomes available, thus allowing the Princess NPC to arrive as well.
 * The Truffle begins selling the Autohammer, used to craft Shroomite Bars and upgrade Rockets.
 * The Traveling Merchant begins selling the Pulse Bow.
 * The Witch Doctor begins selling several items related to minion summoning ( some items additionally require a Pygmy Staff), as well as the Vial of Venom.
 * Butcher, Nailhead, Deadly Sphere, Psycho, Mothron, and Dr. Man Fly will start spawning during the Solar Eclipse event.
 * The starts spawning in the Hallow, allowing the  to be summoned.

Tips

 * Excavate a sizable area to allow easier dodging before summoning Plantera.
 * Widening a Bee Hive in the Underground Jungle is a fast and effective way of making an arena for fighting Plantera (though care should be taken around the Larva).
 * Make sure the area has no background walls. This will significantly reduce Plantera's mobility in the second form as she does not have walls to hook onto.
 * Living Fire Blocks work excellently for lighting up the arena in place of torches; Plantera cannot grab onto them.
 * Using a Gravitation Potion can help the player avoid damage from Thorn Balls laying on the ground, as the Thorn Balls obey gravity and fall to the floor. Alternatively, the player can use an arena that has a large empty area at the bottom for Thorn Balls to bounce in, well below the player and out of harm's way.
 * Plantera's Bulbs can spawn in player-made Jungle biomes, which can provide a slightly easier way to fight Plantera.
 * Narrow passages slow Plantera as it takes more time for her to grip the surrounding terrain.
 * The use of a Hellevator combined with wings can make the Plantera fight drastically easier by spawning Plantera at a higher point in the Underground Jungle, and gliding downward while using a ranged or magic weapon.
 * In Plantera's second form, her only ranged attack consists of the Spores which are very easy to kill. This means that keeping distance is key to avoid damage.
 * Making a certain type of arena using teleporters and dart traps, you can escape Plantera's ranged and melee attacks while still shooting arrows or bullets at her.

Trivia

 * The name "Plantera" is a play on the title of the former American groove metal band from the 1990s named, which is Cenx's favorite band. Plantera drops a hamaxe named "The Axe", that looks like a electric guitar. This boss and her drop is a tribute to Pantera guitarist . Also, the achievement for defeating Plantera is called "The Great Southern Plantkill" in reference to Pantera's eighth studio album , and their song named "The Great Southern Trendkill", both released mid 1996. Plantera's boss music is also metal-themed.
 * On the, the saving icon is one of the Thorn Balls that Plantera fires.
 * Plantera has the largest amount of drops in the game, beating even the Queen Bee at 16.
 * Plantera is one of 6 bosses with exclusive music, the others being, , Duke Fishron, , and Queen Bee.
 * Plantera was also the first boss to have exclusive music, having her own music ever since she was added.
 * Plantera appears to be an overgrown flower with its petals shut in her first phase, while the Spores are snapdragons with their petals shut.
 * According to Cenx, Plantera is female.
 * Plantera and the Empress of Light have the only musical instrument drops of any boss, with The Axe and the having the same drop chance as well.
 * Coincidentally, both are female bosses with enraged forms.
 * If including the, Plantera gives access to the most pet-summoning items of any boss, these being the Mud Bud, Seedling, and.
 * Parts of the Jungle Day theme can be heard in Plantera's boss music.
 * The Otherworldly music used for Plantera is named "Rage of Tarunnk" in the official soundtrack of Terraria: Otherworld.