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