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.
Defeat 50 Snowcaps.
Defeat 50 Hayrots.
Vanquish the Grove's Clutch.
Obtain the Silversword
Arrive in Winter Glade.
Defeat 50 Glomps.
Defeat the Rotberg once.
Take the Lift to Autumn Town
Defeat 50 Shelled Oozes.
Defeat the Octopihi once.
Obtain the Flute.
Defeat 50 Acorns.
Upgrade a jar to Grade 4.
Upgrade a tool to Grade 4.
Roll 100 times.
Complete Goldie's Favor.
Reach the Summer Bar
Defeat the Bookworm once.
Defeat 150 Enemies.
Reduce the Rot Dummy to rubble.
Wake up in Spring Hamlet.