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. She can spawn a fair distance off-screen. The bulbs can only break if the blocks under it are broken, or it is mined with a pickaxe.

Attacks
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.

First form
Plantera creeps after the player, firing pink Seeds with increasing speed as she takes more damage. When below 80% health ( / ), she begins dispensing bouncing Thorn Balls and firing green Poison Seeds.

Although Plantera attacks at range, contact can still occur if she gets too close, causing damage.

Second form
Once Plantera is brought down to half of her maximum health, she changes to her second form: her pink petals fall away to reveal a thorn-filled mouth. In this form, Plantera moves more aggressively and attempts to make contact. She also sprouts additional mouths that are attached via vines (called "Plantera's Tentacles") to her body. Once all of the tentacles have been killed, they will never regrow, making Plantera much easier to fight.

Plantera will also release floating pink spore projectiles that drift towards the player, similar to the spores released by the Giant Fungi Bulb.

Enraged behavior
Plantera only 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. Plantera's behavior returns to normal upon re-entry of the Underground Jungle biome.

Attack types

 * Plantera's Hook.png Plantera's Hooks: The ends of Plantera's tentacles, which cling to surfaces and deal damage on contact.
 * Plantera Seed (animated).gif Poison Seed (animated).gif Seeds (first stage): Similar to the stingers of the Hornets and petals of Flower Pow. In expert mode, these can travel through blocks. The green Poison Seeds are more deadly than the more frequently fired pink Seeds, but are not fired until Plantera's health depletes past 80% life ( / ), similar to the Thorn Balls. Pink and green Seeds deal 44 / and 54 /  damage respectively.
 * Thorn Ball.png Thorn Balls (first stage): Thorn Balls are similar to the Spiky Ball weapon. They bounce around erratically and can overwhelm the player if they stay in the same area for too long, as well as dealing 62 / damage on contact. Plantera will not begin releasing Thorn Balls until she drops below 80% of her life ( / ). She will stop releasing the Thorn Balls once she enters the second stage, although the Thorn Balls previously released may linger for a bit.
 * Plantera's Tentacle.png Plantera's Tentacles (second stage): Gnawing minions on "leashes", akin to smaller versions of The Hungry. They deal damage and get in the way of the player's attacks, making piercing weapons more valuable. With  life they are relatively weak and easily killed with proper equipment.
 * Spore.png Spores (second stage): Similar to the Fungi Spores fired by the Giant Fungi Bulb, traveling through blocks. Easily destroyed, similar to Burning Spheres and Water Spheres, but deal damage if touched.

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

Phase 1
Plantera's Seeds, that originally did not travel through blocks, now can and deal increased damage. They also have limited homing capabilities.

The Thorn Balls are also more common and home in on the player.

Phase 2
Plantera's Tentacles, originally only attached to the body, now are attached to the Hooks and have increased in number (considering there are 3 more for each hook, there appear to be 9 extra tentacles). They also have more health than usual (including the default increased health). Plantera's body also does more damage and is faster than normal.

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 no longer require molds.

A status message saying "" will appear, 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:
 * Hardmode Crimson, Corruption, and Hallow spread is slowed to 1/2 (50%) of their previous 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.
 * The Truffle begins selling the Autohammer, used to craft Shroomite Bars.
 * The Traveling Merchant begins selling the Pulse Bow.
 * The Witch Doctor begins selling several items related to minion summoning (as of 1.4 no longer requires Pygmy Staff), as well as the Vial of Venom.
 * Butcher, Nailhead, Deadly Sphere, Psycho and Dr. Man Fly will start spawning during the Solar Eclipse event.
 * The Prismatic Lacewing starts spawning in the Hallow allowing the Empress of Light 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 (but watch out for the Larva unless you want to intentionally summon Queen Bee).
 * 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 which 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 jungle, and gliding downward while using a ranged weapon.
 * In Plantera's second form, her only ranged attack consists of the Spores which are very easy to kill. This means as long as the player maintains their distance, they could kill her while taking little to no damage as long as they have a decently-sized arena.
 * For players on the, it is a good idea to keep the Temple Key for crafting Biome Keys, and enter the Jungle Temple with Actuators instead.

Trivia

 * The name "Plantera" is a play on the title of the former American groove metal band from the 1990's 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, surpassing even the Queen Bee at 19.
 * Plantera is one of 6 bosses with exclusive music, the others being the Queen Slime, Empress of Light, Duke Fishron and Moon Lord.
 * 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 Stellar Tune having the same drop chance as well.
 * Coincidentally, both are female bosses with enraged forms.