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