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
Reach level 100
The Loot Hero have appeared 50 times
Buy 25 garden expansions
The Loot Hero have appeared 25 times
Have bought a total of 100 animals
Reach level 50
Grab gold 1000 times from the Loot Hero
Scare away 500 birds
The Loot Hero have appeared 5 times
Grab gold 500 times from the Loot Hero
Have planted a total of 100 trees
The Loot Hero bashed a mean critter!
Grab gold 100 times from the Loot Hero
The Loot Hero has appeared!
Collect 500 butterflies
Gather 1M Gold
Scare away 100 wolves
Have planted a total of 100 bushes
Have planted a total of 100 plants
Buy 15 garden expansions
Scare away 100 foxes
Gather 100k Gold
Scare away 100 bunnies
Bash 50 moles
Buy 5 garden expansions
Gather 10k Gold
Trash 10 items
Reach level 10