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 Glomps.
Complete Goldie's Favor.
Vanquish the Grove's Clutch.
Defeat 50 Hayrots.
Obtain the Silversword
Roll 100 times.
Arrive in Winter Glade.
Upgrade a jar to Grade 4.
Defeat 50 Acorns.
Upgrade a tool to Grade 4.
Defeat 50 Shelled Oozes.
Obtain the Flute.
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.
Wake up in Spring Hamlet.