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