Here is the full list of all 29 Plantera achievements. It takes around 6-8 hours to unlock all of the achievements on Windows.
Collect 10 ladybugs
The Loot Hero have appeared 50 times
Grab gold 1000 times from the Loot Hero
The Loot Hero have appeared 25 times
Grab gold 500 times from the Loot Hero
The Loot Hero have appeared 5 times
Grab gold 100 times from the Loot Hero
The Loot Hero bashed a mean critter!
The Loot Hero has appeared!
Have planted a total of 100 bushes
Have bought a total of 100 animals
Have planted a total of 100 plants
Have planted a total of 100 trees
Buy 25 garden expansions
Reach level 100
Scare away 100 foxes
Reach level 50
Scare away 500 birds
Collect 500 butterflies
Gather 1M Gold
Buy 15 garden expansions
Gather 100k Gold
Scare away 100 wolves
Bash 50 moles
Scare away 100 bunnies
Gather 10k Gold
Buy 5 garden expansions
Reach level 10
Trash 10 items