Plantera is a moderately hard boss; it can spawn after defeating all three of the mechanical hardmode bosses and destroying one of Plantera's Bulbs in the Underground Jungle.
First, Plantera has plenty of health to chew through, and a good amount of damage, so it would be best to set up a Heart Statue and Star Statue if you use magic. Set them to 1 second timers. Add a Heart Lantern and Campfire to boost your health regeneration further, and a Crystal Ball if you use magic, an Ammo Box for ranged, or a Sharpening Station if you use melee. A Bewitching Table can't hurt no matter what you use. If your arena is fairly large, try to set up more than one healing station like this, so that you can run in a big circle (or oval) and collect hearts on both ends of the loop. Alternately you can setup a house for the nurse for a mid-battle heal.
The actual shape of your arena depends on how you want to fight. For a player who wants to have plenty of evasive space, excavating around a screen's worth of space inside the Underground Jungle and filling it with rows of platforms can work well. For more aggressive players, a smaller space excavated right next to a bulb can work too. Others will just use a stack of bombs to excavate a large area for flying and grappling. Plantera's spike balls do some significant damage and are used frequently during Plantera's first phase, however they can only bounce off solid surfaces, if you don't mind taking the extra time, consider digging a hole at least 2 times deeper than you would use for the fight and stick to the top half of your arena, without the added threat of Plantera's spike balls, it is much easier to defeat.
Honey can be used for its regeneration, so you can make little pools for the regeneration benefit.
Bring a hammer to remove the jungle walls so that in Plantera's second phase, the hooks can only grapple on to the blocks so it cannot grab you with its hooks, and thus you do not take damage from them.
More specific strategies are available below. Some of these have their own arena setups.
Gearing Up
Armor
At the very, very minimum, players should use Hallowed Armor with the helmet to suit their class. Melee characters should use Turtle Armor or Frost Armor. However, equipping a Hallowed Mask instead of the Turtle Helmet offers greater defense and melee critical strike chance, only sacrificing the relatively decent Turtle Armor set bonus. Ranged characters should use Chlorophyte armor or Frost Armor. Magic users should also use Chlorophyte armor. You can use Chlorophyte armor's bonus with the Leaf Crystal for melee damage to help with attacking purposes. If players are farming plantera, using Vampire knives and Frost Armor can keep you alive and drain Plantera's health.
Weapons
Generally, you should use a Bewitching Table and a Summoning Potion to increase your minion count to three, and conjure three spiders or three pairs of mini twins. Despite their higher damage, pirates are not the best choice due to their lack of flying. Those minions will give you a decent base DPS, allowing you to focus less on your damage output and more on dodging.
Melee
- Spears work well as they can attack through blocks and can strike multiple times in one swing. The Chlorophyte Partisan is especially convenient as it shoots a small projectile that hits multiple times, making it a very useful spear for this fight. The Mushroom Spear is also a great option due to the spinning mushrooms it spawns. Keep using it and you can defeat Plantera in about 2-3 minutes.
- Swords like the Terra Blade, True Night's Edge or Frostbrand are fine choices for high ranged damage.
- The Death Sickle has proven to be a great weapon.
- The Cutlass or the Terra Blade combined with the Hallowed Armor can be very effective if the weapon has a good prefix.
- Using the Light Disc proves effective if you have more than one of them and are in a smaller arena.
- The Yelets is very useful, as it can rip through its first phase very quickly.
- "Legendary" modifier Template:Pc iconFetid Baghnakhs are incredible if you're going melee. This will end Plantera within' seconds. To avoid dying, use Turtle armor, Star Veil, and other "Warding" modifier (+4 Defense) accessories. Stacking further attack speed to 51% from accessories and armor by using full Hallowed armor, Mechanical Glove and a Fire Gauntlet (any modifiers) will speed up the fight even further, attacking so fast each swing is cut short, making short enemies like turtles difficult to hit with them. Using an Flask of Ichor also helps significantly. This method doesn't require any mobility accessories once Plantera is in melee range provided you have knockback immunity from a Shield and a Star Veil to help keep you alive for the duration of the fight as you can simply stand still and attack. This works well even on Expert mode.
- The Shadowflame Knife is a good choice as well, since it allows you to keep your distance and afflicts the Shadowflame debuff. Also it bounces, which allows it to have three chances of hitting Plantera instead of being stopped by the biters.
Ranged
- The Uzi is a popular choice, dealing high damage.
- The Megashark with Chlorophyte Bullet can be used for high damage, although Crystal Bullets, Ichor Bullets, Cursed Bullets or Explosive Bullets will get the job done.
- A Chlorophyte Shotbow with Cursed Arrows or Ichor Arrows can be used to great effect.
- The Flamethrower performs admirably against Plantera itself, but becomes devastating against its tentacle-like minions. It should be used as a second weapon, to quickly get rid of leashes.
Magic
- The Nimbus Rod is often useful (even for non-magic users). It can deal continuous damage which can greatly help the fight, especially in vertical arenas.
- Crystal Storm, Cursed Flames, Magical Harp, or Magic Dagger can be used for rapid attacking.
- The Venom Staff performs very, VERY well against plantera, dealing fast, high damage.
- The Rainbow Rod can do well against Plantera.
- Using the golden shower every so often can prove to be very helpful as it inflicts the ichor debuff, increasing your damage input even more.
- The Crystal Serpent can be a good weapon against Plantera.
- If your arena is dug out high enough, the Meteor Staff's rapid targeted damage is very effective.
Potions
- Greater Healing Potions or Template:Mobile iconHorn of Plenty are important for staying alive.
- Ironskin Potions and Regeneration Potions and Mana Regeneration Potions will help you survive much longer.
- Anything that gives the Well Fed buff is welcomed help.
- Increasing damage with buffs from potions such as the Archery Potion, Magic Power Potion, and any Flasks that Plantera is not immune to (Ichor is recommended, or Cursed Flames, if the world has a Corruption) will make an enormous difference.
- Clairvoyance from a Crystal Ball is recommended for magic users.
- Endurance Potions and Wrath Potion are always a great choice as well.
- Using Gravitation Potions and fighting in reversed gravity will mostly negate the threat of Plantera's spiked balls.
Accessories
Wings, and Lightning Boots/Frostspark Boots will allow you to dodge Plantera's attacks.
Damage can be greatly boosted through combat-accessories such as the Warrior/Ranger/Sorcerer/Avenger Emblems. A Moon Stone is also useful.
Charm of Myths can be used for increased regen and reducing the Potion Sickness debuff time from one minute to 45 seconds. A Fire Gauntlet is helpful because of melee damage increase and causing the On Fire! debuff. A Magma Stone can be used as well for this debuff. As with most bosses, the Cross Necklace/Star Veil can be used to extend the invulnerability period after being attacked, allowing you to take less damage.
For Prefixes, damage increasing or critical hit chance increasing Modifiers, such as menacing and lucky, will make a less-than-obvious difference. Melee characters may want to Reforge for modifiers that increase defense, such as warding.
For defensive characters, Flesh Knuckles would be one of the useful items to use. Star Veil would help during the fight during taking damage. Warrior Emblem if you're using melee. Reforging all of the accessories to "Warding" modifier will help too.
The Battle
Plantera will attempt to chase after the player, always trying to make its main bulb overlap the player's space. It moves fairly slowly when compared to a player with speed-boosting equipment. This means a player in a large enough arena can easily keep a distance, assuming they just keep moving. As such, a good arena can make the fight much easier. The second stage begins when Plantera reaches 50% remaining health. The pink petals fall off to reveal a ferocious green maw and Plantera's speed is greatly increased.
Currently, Plantera will enrage and gain more defense, attack more frequently and deals massive amounts of contact and ranged damage if the player leaves the Underground Jungle (including to go to the surface), so surface-level arena strategies are generally obsolete. One exception is taking advantage of Plantera's need to "grapple" to move by building a large enough space that Plantera cannot grapple up after you, and then firing down upon it. However, Plantera can grapple onto backgrounds, and since they go until reaching the underworld, you would have to clear them out first.
The player will want to focus on dodging attacks while shooting constantly at Plantera. Once plantera reaches its second form, the player should be very wary and try to avoid Plantera's lunges.
Ranged characters would also try to kill tentacles as soon as they appear. Due to generally low defense of ranger's sets, getting caught by them often will kill player really fast.
Attack types
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Seeds | Phase 1 | Frequently spits projectiles similar to the stingers of the Hornets. Easily avoided in Normal mode if the player hides behind blocks. |
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Thorn Balls | Spiky balls similar to the Spike Ball weapon. They linger on the ground for a significant amount of time and deal around 50 damage. These balls fall through platforms, so use of platforms in an arena is recommended. They are however also incredibly bouncy and can easily reach players some height in the air. | |
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Hooks | Plantera uses three vines for its locomotion, apparently larger versions of the Ivy Whip. The ends of these vines deal damage if the player touches them. | |
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Biters | Phase 2 | Once Plantera begins the second stage it will sprout a large number of small gnawing minions on "leashes". They simply wave themselves around at the end of their leash and get in the way of the player's attacks, making piercing weapons more valuable. They are fairly strong and easily killed. |
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Spores | Phase 2 | Frequently spits projectiles similar to the Fungi Spores fired by the Giant Fungi Bulb. Easily destroyed and avoidable, but deals high damage if hit. |
Specific Strategies
The Teleportation Trick
Teleportation trick
Make a long hallway (preferably longer than 150 tiles, but still shorter than 250 due to the bug shown below, because of Plantera's movement speed in the second phase) out of any material you desire, and place a Teleporter on each end, and wire them together. Test it first. Then, summon Plantera.This strategy works out with Frost armor or Hallowed armor,a Megashark with Crystal Bullets, with the ironskin, regeneration,well fed and thorns buff.Using a Flamethrower is not recommended since it has a short range compared to other guns, and it won't be against the biters since the crystal bullets will take care of them.
When it's climbing down toward you on one side, flip the trigger used to activate Teleporter. You will teleport to the other side, and Plantera will have to climb back at you. It is even possible to combine the Teleporters with a Timer to remove the need to activate a trigger or with a Pressure Plate,which will only require the player to jump for teleporting.
Boomerang type weapons can fly indefinitely when using a teleportation trick. Before the boomerang returns, the player can teleport to the other end of the hall, and the boomerang will change directions and pierce enemies along the way.
Note that if the hallway is too long, Plantera will despawn. This was observed in a hallway as small as 200 tiles.
Ring Around the Rosey method
It is little known that Plantera's AI can be manipulated to be trapped inside of a block for the first stage as the player flies around it. First, a standard arena must be built (15-20 tiles high and about 50 tiles long) then, around the middle, a floating 7x7 block must be built, leaving room for the player to fly around it while just being able to shoot Plantera (preferably with a Terra Blade or Flamethrower) this will take it into second stage often without taking any hits. Second stage gets a little more intense. This means that the block idea could be discarded for the remainder of the fight, unless the player feels confident enough to keep Plantera inside.
Waterbolt method
This method is simple, but needs strong armor, and a friend. Create two small boxes (preferably 6x6), and add teleporters to each and wire them up. Add a trigger, and you are done. Summon Plantera, get into one of the boxes, and use your water bolt inside the box. The projectiles will damage Plantera, and if you feel overwhelmed, teleport to the other box, and keep going. This strategy does not require much preparations, but this requires at least chlorophyte armor. So, this is a good way to kill Plantera if you have good armor, good skills, and a good friend to help you.
Hellevator method
Simple to execute and blocks most of Plantera abilities but not for melee users. Dig vertical two block wide shaft through the jungle. After breaking the bulb, run to the shaft and start ascending letting Plantera chase you. Just keep your distance and shoot away. If low on health, run out of Plantera's reach and wait for potion cooldown. When approaching the surface, drop down past Plantera and start descending in the same way.
Spawn Point Method
This method only works on the 
Console version. Simply build a house in the underground Jungle, set your spawn point and destroy the bulb. Run into the house and wait next to the bed, being careful not to let Plantera despawn. Equip an auto-swinging sword. Recommendations are Excalibur, Cutlass or a well reforged Chlorophyte Saber. If you are killed you will respawn in the house where Plantera is. Let Plantera sit on top of you while you slash it with the sword. This will make Plantera farming relatively easy.
