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