Here is the full list of all 21 Garden Story achievements. It takes around 12-15 hours to unlock all of the achievements on Windows.
Vanquish the Grove's Clutch.
Defeat 50 Snowcaps.
Defeat 50 Glomps.
Defeat 50 Hayrots.
Defeat 50 Shelled Oozes.
Complete Goldie's Favor.
Upgrade a jar to Grade 4.
Obtain the Flute.
Obtain the Silversword
Arrive in Winter Glade.
Upgrade a tool to Grade 4.
Defeat 50 Acorns.
Defeat the Rotberg once.
Take the Lift to Autumn Town
Defeat the Octopihi once.
Reach the Summer Bar
Defeat the Bookworm once.
Defeat 150 Enemies.
Reduce the Rot Dummy to rubble.
Roll 100 times.
Wake up in Spring Hamlet.